Received: by nummer-3.proteosys id <01C19443.3E56336C@nummer-3.proteosys>; Thu, 3 Jan 2002 11:41:47 +0100 Return-Path: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C19443.3E56336C" x-vm-v5-data: ([nil nil nil nil nil nil t t nil][nil nil nil nil nil nil nil nil nil nil nil nil "^From:" nil nil nil]) X-MimeOLE: Produced By Microsoft Exchange V6.5 x-vm-vheader: ("From:" "Sender:" "Resent-From" "To:" "Apparently-To:" "Cc:" "Subject:" "Date:" "Resent-Date:") nil x-vm-bookmark: 1 Content-class: urn:content-classes:message Subject: Citations and reference-lists Date: Fri, 1 Mar 1991 22:35:59 +0100 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: From: "LaTeX-L Mailing list" Sender: To: "Rainer M. Schoepf" Reply-To: "LaTeX-L Mailing list" Status: R X-Status: X-Keywords: X-UID: 295 This is a multi-part message in MIME format. ------_=_NextPart_001_01C19443.3E56336C Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable % You probably don't remember my mail of 9th October, in which I said % there might need to be separate interfaces for "reference by % number", author-date and "short form". [I'll have a go % at suggesting what these might be in a future message.] % Well, this is the "future message" containing "the go". Sorry for = the % delay. % % This is a LaTeX 2.09 input file partly because its rather long, and = partly % so that Malcolm can lift it for TeXline if he's still on the lookout = for % articles (and doesn't mind a long one). Hence, some of the wording = is aimed % at a possible TeXline audience. % % Comments are particularly invited from people who have practical % experience of the "short form" scheme, since I've not used that = scheme % seriously myself. % % David Rhead % (JANET: d.rhead@uk.ac.nottingham.ccc.vme) % \documentstyle[11pt]{article} \newcommand{\itlatex} {L\kern-.30em\raise.3ex\hbox{\footnotesize\it A}\kern-.15em T\kern-.1667em\lower.7ex\hbox{E}\kern-.100emX} % For italic = in refs \newcommand{\BibTeX} {{\rm B\kern-.05em{\sc i\kern-.025em b}\kern-.08em T\kern-.1667em\lower.7ex\hbox{E}\kern-.125emX}} \newcommand{\ttbackslash}{\symbol{92}} \begin{document} \title{How might \LaTeX\ 3.0 deal with citations and reference-lists?} \author{David Rhead \\ Nottingham University} \date{} \maketitle \tableofcontents \sloppy \section{Introduction} Since there are now plans for a new version of \LaTeX\ \cite{lamport,mittelbach}, this may be a good time to consider how a future version should deal with citations and reference-lists. My viewpoint is that of an advisor to authors who use \LaTeX\ 2.09. As such, I'm often in the position of having to decide whether \LaTeX\ acts inappropriately or whether an author is asking for something inappropriate. Generally, I have the impression that \LaTeX\ 2.09 = sometimes makes it unnecessarily difficult for people to comply with the = conventions that are standard in \lq\lq academic publishing''. In making the suggestions that follow, I do realise that it's easier for = me to suggest that the volunteers developing \LaTeX\ 3.0 might provide some = new facilities than it is for a volunteer to find time to do the work! I assume that the reader is familiar with the relevant sections of \cite{lamport}. \section{Conventions to be supported} \label{conventions} \subsection{Citation schemes} \label{basic-schemes} In mainstream publishing \cite{bs-5605,bs-6371,butcher,chicago,gibaldi,huth,inter,iso-690,oconnor,= page}, there seem to be three basic schemes for citations and the corresponding reference-lists: \begin{description} \item[reference by number] In this scheme, citations are normally = numbered in order of first citation. In particular, \lq\lq order of first = citation'' is used by over 300 biomedical journals \cite{huth,inter}, and is specified in the ISO standard \cite{iso-690}. (Thus, in \BibTeX\ = terms, the usual numbering sequence is that given by {\tt unsrt}.) The = number is used as a \lq\lq label'' in the reference-list. \item[author-date] There are two main forms of citation, depending on = whether or not the cited author's name occurs naturally in a sentence. In = the first case, the citation is of the form \lq\lq\ \dots\ (1972) \dots\ '', whereas in the second case it is of the form \lq\lq\ = \dots\ (Crane, 1972) \dots\ ''. There are no \lq\lq labels'' in the reference-list, which is arranged in alphabetical order of = authors' surnames (with supplementary rules for \lq\lq tie-breaking''). \item[short form] The \lq\lq short form'' scheme is often used when = citations occur in footnotes. Typically, the first citation (or the first citation in the current chapter) gives a fairly full reference but subsequent citations use a short form. The \lq\lq short form'' = may be introduced within the first citation, or given in a table of abbreviations. There are no \lq\lq labels'' in the = reference-list, which may be subdivided by \lq\lq type of cited document''. The scheme is common in the humanities, but also seems to be used = by some software-houses when referring to their own publications = (see, for example, \cite{norusis}). \end{description} I think that, in order to make it straightforward to achieve, with = \LaTeX, the effects that people routinely achieve with traditional publishing procedures, it is desirable that \LaTeX\ should provide explicit support = for all three citation schemes. Notice that: \begin{itemize} \item It is not, in general, possible to convert a document from one = scheme to another (e.g., from \lq\lq reference by number'' to = author-date) automatically. Some re-writing is required. \item The number of items of information that need to be available differ between the schemes. For a \lq\lq reference by number'' citation, it is only necessary to keep track of one item (the number), whereas for the other schemes it is necessary to = keep track of more than one item (i.e., the author and the date, or the \lq\lq fairly full form'' and the \lq\lq short form'') so that they can be used separately. \item Occasionally, two different schemes may be used in parallel within the same document. (For example, in \cite{norusis}, a software-house seems to use \lq\lq short form'' when citing its own publications, but author-date when citing other = publications.) \end{itemize} Thus, it seems to me that the three schemes are best regarded as = logically distinct. However, within a particular scheme, there are variations of = punctuation, etc., that can be regarded as matters of \lq\lq house style''. For example, some journals that have adopted a \lq\lq reference by = number'' scheme use bracketed numerals for citations, while others use = superscripts. Such variations can be accomodated by differences between style files. \subsection{Additional references} \label{support-additional} In addition to a list of \lq\lq works cited'', some documents have an additional reference-list that specifies \lq\lq further = reading'' or \lq\lq all sources consulted'' (see \cite[pp.\ 182 \& 192]{butcher}, \cite[p.\ 40]{huth} and \cite[p.\ 22]{bs-4821}). There needs to be some provision for typesetting such additional lists. \section{Deficiencies in \LaTeX\ 2.09} \label{2.09-problems} \subsection{Citations} \label{2.09-citations} When used in conjunction with \BibTeX\ and = \verb+\bibliographystyle{unsrt}+, \LaTeX\ 2.09 makes a good job of organising citations (and sorting the corresponding reference-list) according to the \lq\lq reference by = number'' scheme as required by many journals. Generally, however, \LaTeX\ 2.09 does not provide the breadth or depth of facilities needed to support the variety of requirements for mainstream publishing: \begin{itemize} \item It is unfortunate that the \lq\lq reference by number'' sequence = obtained most naturally by the do-it-yourself-er \cite[p.\ 73]{lamport} = from \LaTeX\ 2.09 (\lq\lq order of appearance within {\tt = thebibliography}'') is unlikely to be what the do-it-yourself-er's journal-editor = requires (which will usually be \lq\lq order of first citation''). The do-it-yourself-er is given no warning (either in \cite{lamport} or = by the software) that sorting is likely to be needed. \item Although one can use style-options such as {\tt apalike} and {\tt aaai} to re-define \verb+\cite+ and {\tt thebibliography} for an author-date scheme, there are many obstacles placed in the user's way: \begin{itemize} \item The existence of the style-options is not documented in \cite{lamport}. \item If one finds a style-option in a (software) archive, it may need modification to produce the precise effect = required. \item It is not obvious how one should refer separately to two items (author and date) supplied via a \verb+\bibitem+ = argument originally designed for one. The do-it-yourself-er might have to study style files such as {\tt aaai.sty} and {\tt = bbl} files such as those produced by {\tt aaai-named.bst} to deduce how to do this. \end{itemize} \item The \lq\lq short form'' scheme seems unsupported. \item At certain points in a document, an author my need to cite several works at once. It may be necessary to specify a page (or section, etc\@.) for each work. For instance, \cite[p.\ 404]{chicago} suggests references of the form \lq\lq (Kelley 1896a, 10; Kelley 1896b; Kelley 1907, 3)''. This is not easy in \LaTeX\ 2.09, since \verb+\cite+'s optional argument applies to the citation as a whole. The author cannot supply a separate \lq\lq optional argument'' for each work. (By contrast, {\sf EndNote}'s analogous facilities \cite[p.\ 58]{endnote} seem to allow each individual work to be given its own \lq\lq additional text''.) \item It does not seem easy to use different schemes in parallel within the same document. If \verb+\cite+ and {\tt thebibliography} are defined as required for one scheme, they will usually be unsuitable for any other. \end{itemize} \subsection{Additional references} \label{2.09-additional} As stated in section \ref{support-additional} an author may need to typeset a list of \lq\lq further reading'' etc., in addition to the usual list of \lq\lq works cited''. If using the {\tt thebibliography} environment from one of \LaTeX\ 2.09's standard styles for such additional references, an author will be faced with the following problems: \begin{itemize} \item the title will be the same as that for the list of \lq\lq works cited'', namely \lq\lq References'' for {\tt article} and \lq\lq Bibliography'' for {\tt report} and {\tt book} \item the \lq\lq labels'' (which may be appropriate in the list of \lq\lq works cited'', particularly for the \lq\lq reference by number'' scheme) will also appear in the additional list (where they are inappropriate), because both lists use the same definition of \verb+\bibitem+ \item by default, the \lq\lq labels'' will not be unique, since the \lq\lq works cited'' list and the \lq\lq additional = references'' list will both be numbered from one \item it will be necessary to supply dummy {\it cite-key\/}s, purely to satisfy the syntax required for a \verb+\bibitem+. \end{itemize} \subsection{Other problems} \label{2.09-other} The definitions of the {\tt thebibliography} environment in \LaTeX\ 2.09's standard styles: \begin{itemize} \item issue either a \verb+\section*+ or a \verb+\chapter*+ command, using a {\it heading} of \lq\lq References'' for {\tt article} and \lq\lq Bibliography'' for {\tt report} and {\tt book} \item set {\it left-head\/} and {\it right-head\/} to either \lq\lq REFERENCES'' or \lq\lq BIBLIOGRAPHY'' \item do not arrange for a table-of-contents entry. \end{itemize} These definitions can cause problems when the {\it heading}, etc.\ supplied by the standard style is inappropriate, or when a = table-of-contents entry is desired. Admittedly, anyone who doesn't like the standard styles is free to take copies of the style files and modify them to suit their = requirements. However, I have the impression that: \begin{itemize} \item among people who are competent to modify style files, modification of these aspects of the standard styles is \lq\lq the rule'' rather than \lq\lq the exception'' \item those \LaTeX\ users who aren't particularly computer-literate find the whole business mysterious, and seek out support staff who have to modify these aspects of the style files for them. \end{itemize} Overall, this seems to be an area where \LaTeX\ 2.09 is failing to \lq\lq free people from formatting concerns to allow them to concentrate on writing'' \cite[p.\ 8]{lamport}. An associated problem is that modified style files may no longer be compatible with standard utilities such as {\tt lablst}. \section{Introduction of new facilities} \label{new-facils} It has been decided \cite{mittelbach} that \LaTeX\ 3.0 will be = compatible with \LaTeX\ 2.09 input files. Thus, in particular, \LaTeX\ 3.0 must define \verb+\cite+ and \verb+thebibliography+ so that they have the same = effect on \LaTeX\ 2.09 input files as the \LaTeX\ 2.09 definitions do. This = implies that it would be difficult for \LaTeX\ 3.0 to (for example) define = \verb+\cite+ so that there can be an optional argument for each work in a multiple = citation and define \verb+\bibitem+ so that it can have an \lq\lq author'' = argument and a \lq\lq date'' argument. It therefore seems best to provide duplicates of the \LaTeX\ 2.09 = facilities in \LaTeX\ 3.0 (for \lq\lq backwards compatibility'') but to attempt to provide new commands/environments in parallel so as to provide the = required functionality. The new facilities would be regarded as the \lq\lq = normal'' facilities, would be described in the body of the successor to = \cite{lamport}, and would be the natural choice for new users. The old facilities would be regarded as \lq\lq deprecated'' and relegated to an appendix of the = successor to \cite{lamport}. Thus we can have both backwards compatibility and improved facilities for the future. \section{Division of labour} \label{div-of-labour} \subsection{Details needed for document \lq\lq as a whole''} The three basic citation schemes mentioned in section = \ref{basic-schemes} determine certain details of a document \lq\lq as a whole''. For each citation, there must be an entry in a reference-list. Each entry in the relevant reference-list must have associated information that can be used in citations. \subsection{Details needed for reference-list, etc.} There are a lot of other details that need to be resolved. The information within each reference-list entry will probably need formatting according to certain rules of \lq\lq house style''. The information given in citations needs organising in a consistent way (particularly for the \lq\lq short form'' scheme). Different people may want to assemble their reference-lists in different = ways. Some people may wish to \lq\lq do it themselves'' \cite[p.\ 73]{lamport} = from a physical card-index, while some may prefer to use \BibTeX\ to get = details >from a {\tt bib} file. In some disciplines, proprietary systems such = as {\tt EndNote} \cite{endnote} seem popular (because they help the user to = search a database for literature to cite, as well as helping the user incorporate details of the literature into a document). Researchers may also wish to incorporate material obtained by searching details held on a {\sc cd-rom}. A reference-list generally needs sorting into a particular order. Since = the list may occupy several pages, I assume that any sorting is best done = outside \LaTeX, either by other software (e.g., \BibTeX) or manually by the = author. \subsection{\LaTeX\ and other software} It seems best to regard the movement of text-strings (e.g., an author's surname) within the \lq\lq document as a whole'' as a task that is = distinct >from the arrangement of details within the text-strings, and to assume = a \lq\lq division of labour'' in which the former task is performed by = \LaTeX\ while the latter is performed by some other software or manually by the = author. The \lq\lq division of labour'' between \LaTeX\ 2.09 and \BibTeX\ seems = to set a good precedent. This division of labour will lead to modular software. Once the interface between a reference-list and the rest of the document has been defined, people can use \LaTeX\ for the body of their document, but can: \begin{itemize} \item experiment with different software (\BibTeX, {\sf EndNote}) for formatting the details of their reference-lists \item enhance the other software (e.g., \BibTeX) independently of enhancements to \LaTeX. \item lay their reference-lists out manually if they prefer. \end{itemize} \section{\protect\LaTeX\ 3.0: A possible user interface?} \label{what-to-do} \subsection{Specifications and names} If the reasoning given in sections \ref{conventions}, \ref{new-facils} and \ref{div-of-labour} is accepted, consideration needs to be given to the form that new commands/environments should take in order to support = the three basic citation schemes, and to provide facilities for \lq\lq = additional references''. In particular, it will be necessary to choose names other than \verb+\cite+, {\tt thebibliography} and \verb+\bibitem+ = (since these names will be kept for the facilities provided for compatibility = with \LaTeX\ 2.09). \subsection{Four sets of commands/environments} \label{4-sets} It seems to me that it would probably be convenient to have three sets = of commands/environments for dealing with citations and the corresponding reference-lists, each set specifically designed to implement a = particular citation scheme. Having three such sets gives scope for taking proper account of the peculiarities of each scheme, without having one scheme adversely affected by the peculiarities of another. To avoid the difficulties mentioned in section \ref{2.09-additional}, it might also be worth having a specific environment for \lq\lq additional references''. \LaTeX\ 3.0 might, for example, have commands/environments as specified in the following table. \begin{center} \begin{footnotesize} \renewcommand{\arraystretch}{1.25} \begin{tabular}{lccccccc} \hline & Citation & Environment for & Entry in = \\ & & reference-list & = reference-list \\ \hline Reference by number & \verb+\numcite+ & {\tt numrefs} & = \verb+\numentry+ \\ \hline Author-date & \verb+\dcite+ & {\tt adrefs} & = \verb+\adentry+ \\ & \verb+\adcite+ & & = \\ \hline Short form & \verb+\firstcite+ & {\tt sfrefs} & = \verb+\sfentry+ \\ & \verb+\sfcite+& & = \\ \hline Additional references& --- & {\tt morerefs} & = \verb+\moreentry+ \\ \hline {\it Analogue at 2.09} & \verb+\cite+ & {\tt thebibliography} & = \verb+\bibitem+ \\ \hline \end{tabular} \end{footnotesize} \end{center} Here it is assumed that: \begin{itemize} \item \verb+\numcite+ and \verb+\numentry+ have {\it key-list} and {\it cite-key} (respectively) as their only mandatory arguments. \item \verb+\dcite+ and \verb+\adcite+ have {\it key-list} as argument. \verb+\dcite+ gives a citation of the form (1972), while \verb+\adcite+ gives a citation of the form (Crane, 1972). \verb+\adentry+ has three arguments: the {\it cite-key}, the author (e.g., Crane), and the date (e.g., 1972). \item \verb+\firstcite+ and \verb+\sfcite+ have {\it key-list} as = argument. \verb+\firstcite+ gives the form of citation to be used when a = work is first mentioned. \verb+\sfcite+ gives the short form to be used in subsequent citations. \verb+\sfentry+ might have 3 arguments: the {\it cite-key}, the = form of reference to be used at the first citation, and the short form to be used subsequently. \end{itemize} Although it would be desirable for the successors to the ``standard = styles'' to define facilities for all three citation schemes, other \verb+\documentstyle+s need not define facilities for all three. For = example, a journal that wants its authors to use the author-date scheme would = supply a style file that only provides author-date facilities. \subsection{Further details} \label{further-details} \subsubsection{Reference by number} The \verb+\numcite+ and \verb+\numentry+ commands might take the form \verb+\numcite{+{\it key-list}\verb+}+ and \verb+\numentry{+{\it cite-key}\verb+}+. Notice that, since = \verb+\numentry+ is specifically designed for \lq\lq reference by number'', there is no = need to allow an optional {\it label} argument like that for \verb+\bibitem+. To conform to the ISO specification \cite{iso-690}, the successors to = the ``standard styles'' would arrange for \verb+\numcite+ to give a citation = of the form (24) and for \verb+\numentry+ to give a reference-list entry of the form \begin{description} \item[{\rm 24.}] {\sc Crane, D.} {\it Invisible colleges.} \dots \end{description} Perhaps \LaTeX\ 3.0 could use the {\tt aux} file to refine an initial = estimate of the width of the final \verb+\numentry+'s \lq\lq label'', so that the do-it-yourself-er wouldn't need to supply a {\it widest-label\/} = argument. \subsubsection{Author-date} The commands \verb+\dcite+, \verb+\adcite+ and \verb+\adentry+ might be defined to have the forms \verb+\dcite{+{\it key-list}\verb+}+, \verb+\adcite{+{\it key-list}\verb+}+ and \verb+\adentry{+{\it cite-key}\verb+}{+{\it author}\verb+}{+{\it = date}\verb+}+. The {\tt adrefs} environment would {\it not} have a {\it widest-label} argument, since in this scheme entries in the reference-list are = unlabelled. If such a definition of \verb+\adentry+ was documented in the successor = to \cite{lamport}, a do-it-yourself-er would be able to use the author-date system just as easily as the \lq\lq reference by number'' system. To conform to the ISO specification \cite{iso-690}, the successors to = the ``standard styles'' would arrange for \verb+\dcite+ to give a citation = of the form (1972), for \verb+\adcite+ to give a citation of the form (Crane, 1972), and for \verb+\adentry+ to give a reference-list entry = with no label. \subsubsection{Short form} The \verb+\firstcite+, \verb+\sfcite+ and \verb+\sfentry+ commands might be defined as \verb+\firstcite{+{\it key-list}\verb+}+, \verb+\sfcite{+{\it key-list}\verb+}+ and \verb+\sfentry{+{\it cite-key}\verb+}[+{\it fairly-full-form}\verb+]{+{\it short-form}\verb+}+. Such definitions would, in effect, automate Butcher's manual method of ensuring consistency \cite[p.\ 178]{butcher}. Since, in some = situations, a reference is given in full when it is first cited \cite[p.\ = 407]{chicago}, the default {\it fairly-full-form} would be the full reference as put in the reference-list by \verb+\sfentry+. The {\tt sfrefs} environment would {\em not} have a {\it widest-label} argument. The successors to the ``standard styles'' would arrange for = \verb+\firstcite+ to produce the {\it fairly-full-form} and \verb+\sfcite+ to produce the {\it short-form}.% \footnote{% This makes the pessimistic assumption that \LaTeX\ can not itself = determine whether a citation is the \lq\lq first citation'' of a particular work. If someone was ingenious enough to produce code that determined whether = a citation is a \lq\lq first citation'', {\tt\ttbackslash firstcite} would = be unnecessary (except, perhaps, for the construction of tables of = abbreviations \cite[p.\ 414]{chicago}.)% } To conform to the ISO specification \cite{iso-690}, neither \verb+\firstcite+ nor \verb+\sfcite+ would add any punctuation (but, for example, a style file that = implemented the MLA conventions would have to add brackets \cite[ch.\ 5]{gibaldi}). In the successors to the ``standard styles'', the \verb+\sfentry+ would produce an entry with no label. People producing other style files would be free to implement other conventions \cite[p.\ 168]{butcher}. Some works may have no bibliography or may have just a \lq\lq select bibliography'' \cite[p.\ 168]{butcher}. For such works, it will still be necessary to supply the details for use by \verb+\firstcite+ and \verb+\sfcite+. It may therefore be worth allowing a form of {\tt sfrefs} (e.g., \verb+\begin{sfrefs}[null]+) that holds details of cited works but does no typesetting. \subsubsection{Additional references} \label{3.0-additional} Since the entries in an \lq\lq additional list'' will not be cited as = such (although an \lq\lq all sources consulted'' list may contain a duplicate = of a cited entry in a \lq\lq works cited'' list), the list will be typeset without \lq\lq labels''. Even in a document that uses the \lq\lq = reference by number'' citation scheme (and so needs \lq\lq labels'' in the {\tt = numrefs} list), there will be no \lq\lq labels'' for the entries in an additional = list. It therefore seems likely that the {\tt morerefs} environment could be implemented as a variation of {\tt adrefs} or {\tt sfrefs}, the main = changes being: \begin{itemize} \item a change of title (but see section \ref{reflist-scope}) \item absence of {\it cite-key, author, date, fairly-full-form} and {\it = short-form} arguments. \end{itemize} \subsection{Order within the reference-list} As stated in section \ref{div-of-labour}, it is probably best to leave any sorting of the reference-list to some other software, or to the = author. However, it might be possible for \LaTeX\ to provide a warning if a reference-list is obviously in the wrong order. Perhaps: \begin{itemize} \item although there may be no easy alternative to numbering \verb+\numcite+s in order of appearance within {\tt numrefs} (even though \lq\lq order of first citation'' is usually what is required), \LaTeX\ could give a warning if a \verb+\numcite+ gave a number that exceeded the \lq\lq biggest number produced by \verb+\numcite+ so far'' by more than one. \item there could be a warning if an \verb+\adentry+ had an {\it author} whose first letter came before the first letter of = the preceding \verb+\adentry+'s {\it author} in the alphabet. \end{itemize} \subsection{Citation of a specific division} \label{division} As stated in section \ref{2.09-citations}, provision needs to be made = for the citation of a particular division (e.g., page, section, chapter, equation) of another work. The syntax of citation commands should not only allow several works to be cited simultaneously, but should also allow the relevant division of each work to be specified. From the author's point-of-view, there would be a variety of = satisfactory ways to specify citations that are to appear as ``[4, p.\ 10; 5; 6, p.\ 3]'', e.g. \begin{verbatim} \numcite{smith[p. 10],brown,jones[p. 3]} \numcite{smith, p. 10; brown; jones, p. 3} \numcite{smith & p. 10; brown; jones & p. 3} \end{verbatim} The precise syntax would have to take account of the practicalities of programming a command that has to be = able to accept pairs of arguments, where the second member of each pair is = optional. Analogous facilities would be needed for author-date and \lq\lq short = form'' citations. Incidentally, since abbreviations such as p., ch., sec., and fig.\ are common when such divisions are specified, I think that citation commands should arrange for the optional arguments to be typeset with \verb+\frenchspacing+. \section{Details of reference-lists} \subsection{Variations within mainstream publishing practice} \label{mainstream-lists} Although many academic and technical publications involve only a single undivided reference-list, some such publications involve: \begin{description} \item[more than one list] This situation can arise: \begin{itemize} \item when there is a list of \lq\lq further reading'' etc., as well as the list of \lq\lq works cited''. This case has been covered in sections = \ref{support-additional}, \ref{2.09-additional}, \ref{4-sets} and = \ref{3.0-additional}. \item when conference proceedings are produced, since each contribution may have its own reference-list. \item in manuals for software. For example, in \cite{norusis}, a software house's own publications are introduced in the = preface and cited (in effect) using a \lq\lq short form'' scheme, = while other people's publications are listed at the end of the = manual and are cited using the author-date scheme. \end{itemize} \item[subdivisions within a list] Some reference-lists, particularly in the humanities, are = subdivided according to the source of the cited documents (see \cite[p.\ 183]{butcher}, \cite[p.\ 425]{chicago} and \cite[p.\ 88]{gibaldi}). \end{description} In some cases, an author may wish to add explanatory paragraphs = describing, for example, how material was chosen for a \lq\lq select bibliography'' \cite[fig.\ 15.11]{chicago} or information about access to (document) archives \cite[fig.\ 15.16]{chicago}. \subsection{\protect\LaTeX\ 2.09} \LaTeX\ 2.09 can cope with documents that have more than one {\tt thebibliography} environment, and seems to deal satisfactorily with a situation in which some \verb+\cite+ commands are to one {\tt thebibliography} and some are to another (provided that the {\it cite-key\/}s are unique). The default effect is to give {\it label\/}s that are not unique, which will be acceptable when each contribution to a \lq\lq conference proceedings'' has its references numbered from one, but not if \lq\lq works cited'' and \lq\lq additional references'' are both numbered from one (see section \ref{2.09-additional}). The specification of {\tt thebibliography} \cite[p.\ 187]{lamport} does not allow anything other than \verb+\bibitem+s within a {\tt thebibliography} environment. Hence, it is not clear how one can introduce subheadings within a reference-list. (In practice, a \verb+\section*+ seems to work between \verb+\bibitem+s, but I suspect that it puts \LaTeX\ 2.09 into a loop if placed before the first \verb+\bibitem+.) Anyone trying to add explanatory paragraphs (as in \cite[fig.\ = 15.11]{chicago} and \cite[fig.\ 15.16]{chicago}) will probably find that \LaTeX\ 2.09 objects that \lq\lq{\verb+Something's wrong--perhaps a missing = \item+}''. \subsection{\protect\LaTeX\ 3.0} Ideally, in order to provide support for the conventions that are = routine in mainstream publishing practice, \LaTeX\ 3.0 should be able to cope = with all the variations outlined in section \ref{mainstream-lists}. \subsubsection{Multiple lists} The suggestions made in section \ref{what-to-do} would probably cater = for most situations where a document has more than one reference-list. The distinction between {\tt morerefs} and the other environments for reference-lists would take care of situations where there is a list of \lq\lq additional references'' as well as a list of \lq\lq works = cited''. The distinction between the \lq\lq short form'' commands/environment and the other commands/environments would take care of situations where = a software house uses \lq\lq short form'' for its own publications and some other scheme for other publications. Conference proceedings will be able to have \lq\lq a reference-list for each contribution'' if \LaTeX\ 3.0 follows the \LaTeX\ 2.09 precedent that allows more than one {\tt thebibliography} in a document. \subsubsection{Subdivisions and explanatory paragraphs} I have the impression that, because the sciences have different = conventions >from the humanities, people using the \lq\lq reference by number'' = citation scheme are unlikely to want the options of subdividing their = reference-list and inserting explanatory paragraphs. Therefore, it would be legitimate = to say (for example) \lq\lq subdivisions and explanatory paragraphs are = supported within {\tt adrefs}, {\tt sfrefs} and {\tt morerefs} but not within {\tt numrefs}'', if this made the programming task easier. For example, it might be convenient to implement {\tt numrefs} as a \lq\lq list-making environment'' (as in \LaTeX\ 2.09) but to implement the other environments in some other way. Lack of support for = subdivisions and explanatory paragraphs is unlikely to matter in {\tt numrefs}; the \lq\lq other way'' (more like \verb+\paragraph+, perhaps?) might make it easier to implement support for these facilities in the other = environments. \subsubsection{Other problems} \label{reflist-scope} One approach to some of the problems mentioned in section = \ref{2.09-other} is for the standard styles to define the heading for the reference-list = by, for example, \verb+\def\numrefsheading{References}+, so that anyone who = wants to change the heading can do so by issuing a \verb+\renewcommand+ = command somewhere before the start of their reference-list. Another approach is to work in terms of the standard publishing industry concept of \lq\lq back matter'' \cite[p.\ 4]{chicago}. Instead of = having to understand where the {\it heading}, {\it left-head}, {\it right-head} = and table-of-contents entry (or lack of it) originate for units such as the glossary (if any), the reference-list(s) and the index (if any) {\em separately}, an author would only have to understand how these = features are treated {\em consistently} within \lq\lq back matter''. Although the \lq\lq back matter'' approach could be used if environments such as {\tt numrefs} followed the {\tt thebibliography} precedent and = issued commands such as \verb+\chapter+ or \verb+\section+ themselves, authors might find the way that {\it heading}, {\it left-head}, {\it right-head} = and table-of-contents entry materialize less mysterious if it was just the = same for a reference-list as for (say) a glossary. This would imply that {\tt numrefs}, {\tt adrefs}, {\tt sfrefs} and {\tt morerefs} should not issue commands like \verb+\chapter+ or \verb+\section+ themselves. As a bonus, it would then be possible for an author to insert an = explanatory paragraph before the reference-list, and to arrange for subdivisions. For example, if there was a {\tt backmatter} environment within which \verb+\chapter+ was treated as defining a unit of \lq\lq back matter'', an author's file might contain commands such as \begin{verbatim} \begin{backmatter} \chapter{Glossary} ... \chapter{References} \section{Primary sources} \begin{sfrefs} ... \end{sfrefs} \section{Secondary sources} \begin{sfrefs} ... \end{sfrefs} \chapter{Further reading} \begin{morerefs} ... \end{morerefs} \end{backmatter} \end{verbatim} \section{Conclusion} \LaTeX\ has a large number of users, and potential users, who wish to = produce documents that conform to the conventions that are standard in academic publishing. One element of their requirement is the need to conform to = the conventions for citations and reference-lists that are usual in their disciplines. The choice for \LaTeX\ 3.0 may be between: \begin{enumerate} \item having more facilities for citations and reference-lists than \LaTeX\ 2.09, perhaps as suggested in section \ref{what-to-do}. This would imply an increase in: \begin{itemize} \item the amount of code needed to implement the facilities, and the guru time needed for writing the code \item the number of pages needed, in the successor to = \cite{lamport}, to describe the facilities --- perhaps 8 pages rather than the 2 pages in \cite{lamport}. \end{itemize} \item no significant increase in the facilities provided for citations and reference-lists. Contrary to the idea of \lq\lq freeing = people from formatting concerns to allow them to concentrate on writing'' \cite[p.\ 8]{lamport}, many authors (perhaps most authors) would = be wasting time: \begin{itemize} \item hacking at style-files \item searching (software) archives for ready made solutions \item taking up support staff's time in the search for advice = (with the support staff in turn taking up gurus' time in their search for = solutions). \end{itemize} Moreover, most of this time would be wasted by (or on behalf of) = authors who don't want anything at all exotic; they just want to conform to the conventions that are standard in traditional academic = publishing. \end{enumerate} I'm inclined to think that the first option would be the lesser of the two evils. \section*{Appendix: Interface with \protect\BibTeX} \addcontentsline{toc}{section}{Appendix: Interface with \protect\BibTeX} The preceding sections make some suggestions for a \LaTeX\ 3.0 user interface that would enable the do-it-yourself-er to conform to the conventions that are usual in academic publishing. It is also necessary to consider the implications for the interface to \BibTeX. \subsection*{Single reference-list} Inspecting {\tt bst} files gives me the impression that, if it was decided to adopt a scheme such as that described in section \ref{what-to-do}, it would be fairly easy to produce new {\tt bst} files to supersede existing ones. For example, a {\tt bst} file that implemented a \lq\lq reference by number'' scheme would write \verb+\numentry+ commands rather than \verb+\bibitem+ commands. If {\tt bst} files were created in this way, they would be able to deal with the straightforward situation when there is a single reference-list that contains all works cited (plus, possibly, any works specified by a command like \verb+\nocite+). \subsection*{Multiple reference-lists, all with the same style} More complicated situations can arise in which a document involves several reference-lists. For example: \begin{itemize} \item The editor of the proceedings of a conference might want the published proceedings to have a reference-list at the end of each chapter. \item If, as suggested in section \ref{reflist-scope}, {\tt sfrefs} was implemented in a way that allowed a sequence of {\tt sfrefs} = environments to each be preceded by a \verb+\section+ command, then, as far as \BibTeX\ is concerned, each {\tt sfrefs} environment might be a = separate reference-list. \end{itemize} In both these examples, the document would involve several = reference-lists, but each reference-list would need to be typeset in a common style. I assume that the main problems would be in arranging: \begin{itemize} \item to have multiple {\tt bbl} files, or distinct divisions of a = single {\tt bbl} file \item that each reference-list takes its entries from the correct {\tt = bbl} file, or from the correct division of a single {\tt bbl} file. \end{itemize} \subsection*{Two reference-lists, each with a different style} People producing documents that have a second reference-list (e.g., \lq\lq further reading'') in addition to the list of \lq\lq works = cited'' might want the first list typeset in one style and the second list typeset in another. (In particular, if the \lq\lq reference by = number'' scheme is used, the first list will have \lq\lq labels'' but the second list will have no \lq\lq labels''.) If the commands/environments = suggested in section \ref{what-to-do} were implemented, the first list would use {\tt numrefs}, {\tt adrefs} or {\tt sfrefs}, while the second list would use {\tt morerefs}. In this situation, it would be necessary to communicate to \BibTeX\ that two lists are required, but that they are to be typeset in = different styles. Since the second list is to contain \lq\lq works {\em not\/} cited'', it will also be necessary to specify the works to be shown in = the second list. If it is decided to extend the interface between \LaTeX\ and \BibTeX\ to cater for such situations, it will probably be necessary to consider defining alternatives to \LaTeX\ 2.09's \verb+\bibliography+ and \verb+\bibliographystyle+ commands, since it seems unlikely that the = syntax of the \LaTeX\ 2.09 commands could be extended so as to pass the = necessary information. One might, for example, consider syntax such as \verb+\bibtexcites[+{\it cites-style}\verb+]{+{\it bib-files}\verb+}+ and \verb+\bibtexmore[+{\it more-style}\verb+]{+{\it bib-files}\verb+}{+{\it key-list}\verb+}+. Here, it is assumed that: \begin{itemize} \item the \verb+\documentstyle+ would set defaults for the {\it = cites-style} and {\it more-style} that are to be passed to \BibTeX, but the = user can over-ride the defaults via the optional arguments to \verb+\bibtexcites+ and \verb+\bibtexmore+ \item \verb+\bibtexmore+'s {\it key-list} argument would be used to specify the works to be included in the list of \lq\lq additional references''. \end{itemize} If it is not practicable to extend the \LaTeX/\BibTeX\ interface to = cater for these situations automatically, it would presumably be a matter of some \lq\lq human intervention'': \begin{itemize} \item to prepare a {\tt bbl} file for the \lq\lq additional references'' \item to \verb+\input+ the {\tt bbl} file. \end{itemize} \begin{thebibliography}{00} \bibitem{lamport} {\sc Leslie Lamport.} {\it \itlatex: A document preparation system.} Addison-Wesley, 1986. \bibitem{mittelbach} {\sc Frank Mittelbach and Rainer Sch\"{o}pf.} With \LaTeX\ into the ninties. {\it TUGboat,} 1989, {\bf 10}, 681--690. \bibitem{bs-5605} {\it Citing publications by bibliographical references.} BS 5605. British Standards Institution, 1978. \bibitem{bs-6371} {\it Citation of unpublished documents.} BS 6371. British Standards Institution, 1983. \bibitem{butcher} {\sc Judith Butcher.} {\it Copy-editing.} Cambridge University Press, 1981. \bibitem{chicago} {\it The Chicago manual of style.} Chicago University Press, 1982. \bibitem{gibaldi} {\sc Joseph Gibaldi and Walter S. Achert.} {\it MLA handbook for writers of research papers.} Modern Language Association of America, 1988. \bibitem{huth} {\sc Edward J. Huth.} {\it Medical style and format.} ISI Press, 1987. \bibitem{inter} {\sc International Committee of Medical Journal Editors.} Uniform requirements for manuscripts submitted to biomedical journals. {\it British Medical Journal,} 1988, {\bf 296}, 401--405. \bibitem{iso-690} {\it Documentation --- bibliographic references --- content, form and structure.} ISO 690. International Organization for Standardization, 1987. \bibitem{oconnor} {\sc Maeve O'Connor.} {\it Editing scientific books and journals.} Pitman Medical, 1978. \bibitem{page} {\sc Gillian Page, Robert Campbell and Jack Meadows.} {\it Journal publishing: principles and practice.} Butterworths, 1987. \bibitem{norusis} {\sc Marija J. Noru\v{s}is.} {\it SPSS-X Introductory Statistics Guide for Release^3.} SPSS Inc., 1988. \bibitem{bs-4821} {\it Presentation of theses and dissertations.} BS 4821. British Standards Institution, 1990. \bibitem{endnote} {\it EndNote: A reference database and bibliography maker.} Berkeley: Niles \& Associates, Inc., 1989. \end{thebibliography} \end{document} ------_=_NextPart_001_01C19443.3E56336C Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Citations and reference-lists

%  You probably don't remember my mail of 9th = October, in which I said
%        there = might need to be separate interfaces for "reference by
%        = number", author-date and "short form".  [I'll have a = go
%        at = suggesting what these might be in a future message.]
%  Well, this is the "future message" = containing "the go".  Sorry for the
%  delay.
%
%  This is a LaTeX 2.09 input file partly = because its rather long, and partly
%  so that Malcolm can lift it for TeXline if = he's still on the lookout for
%  articles (and doesn't mind a long one).  = Hence, some of the wording is aimed
%  at a possible TeXline audience.
%
%  Comments are particularly invited from people = who have practical
%  experience of the "short form" = scheme, since I've not used that scheme
%  seriously myself.
%
%  David Rhead
%  (JANET: = d.rhead@uk.ac.nottingham.ccc.vme)
%
\documentstyle[11pt]{article}

\newcommand{\itlatex}
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    = T\kern-.1667em\lower.7ex\hbox{E}\kern-.100emX}    &nb= sp;  %  For italic in refs
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    = T\kern-.1667em\lower.7ex\hbox{E}\kern-.125emX}}

\newcommand{\ttbackslash}{\symbol{92}}

\begin{document}

\title{How might \LaTeX\ 3.0 deal with citations and = reference-lists?}
\author{David Rhead \\
      Nottingham = University}
\date{}
\maketitle

\tableofcontents

\sloppy


\section{Introduction}

Since there are now plans for a new version of = \LaTeX\
\cite{lamport,mittelbach}, this may be a good time to = consider
how a future version should deal with citations and = reference-lists.

My viewpoint is that of an advisor to authors who use = \LaTeX\ 2.09.
As such, I'm often in the position of having to = decide whether \LaTeX\
acts inappropriately or whether an  author is = asking for something
inappropriate.  Generally, I have the impression = that \LaTeX\ 2.09 sometimes
makes it unnecessarily difficult for people to comply = with the conventions that
are standard in \lq\lq academic publishing''.

In making the suggestions that follow, I do realise = that it's easier for me
to suggest that the volunteers developing \LaTeX\ 3.0 = might provide some new
facilities than it is for a volunteer to find time to = do the work!

I assume that the reader is familiar with the relevant = sections of
\cite{lamport}.

\section{Conventions to be supported}
\label{conventions}

\subsection{Citation schemes}
\label{basic-schemes}

In mainstream publishing
\cite{bs-5605,bs-6371,butcher,chicago,gibaldi,huth,inter,iso-690= ,oconnor,page},
there seem to be three basic schemes for citations = and the corresponding
reference-lists:
\begin{description}
\item[reference by number]  In this scheme, = citations are normally numbered in
      order of first = citation.  In particular, \lq\lq order of first citation''
      is used by over 300 = biomedical journals \cite{huth,inter}, and is
      specified in the ISO = standard \cite{iso-690}.  (Thus, in \BibTeX\ terms,
      the usual numbering = sequence is that given by {\tt unsrt}.)  The number
      is used as a \lq\lq = label'' in the reference-list.
\item[author-date] There are two main forms of = citation, depending on whether
      or not the cited = author's name occurs naturally in a sentence.  In the
      first case, the = citation is of the form \lq\lq\ \dots\ (1972)
      \dots\ '', whereas in = the second case it is of the form \lq\lq\ \dots\
      (Crane, 1972) \dots\ = ''.  There are no \lq\lq labels'' in the
      reference-list, which = is arranged in alphabetical order of authors'
      surnames (with = supplementary rules for \lq\lq tie-breaking'').
\item[short form] The \lq\lq short form'' scheme is = often used when citations
      occur in = footnotes.  Typically, the first citation (or the first
      citation in the = current chapter) gives a fairly full reference but
      subsequent citations = use a short form.  The \lq\lq short form'' may be
      introduced within the = first citation, or given in a table of
      abbreviations.  = There are no \lq\lq labels'' in the reference-list,
      which may be = subdivided by \lq\lq type of cited document''.
      The scheme is common = in the humanities, but also seems to be used by
      some software-houses = when referring to their own publications (see, for
      example, = \cite{norusis}).
\end{description}
I think that, in order to make it straightforward to = achieve, with \LaTeX,
the effects that people routinely achieve with = traditional publishing
procedures, it is desirable that \LaTeX\ should = provide explicit support for
all three citation schemes.

Notice that:
\begin{itemize}
\item It is not, in general, possible to convert a = document from one scheme
      to another (e.g., from = \lq\lq reference by number'' to author-date)
      automatically.  = Some re-writing is required.
\item The number of items of information that need to = be available
      differ between the = schemes.  For a \lq\lq reference by number''
      citation, it is only = necessary to keep track of one item
      (the number), whereas = for the other schemes it is necessary to keep
      track of more than one = item (i.e., the author and the date, or the
      \lq\lq fairly full = form'' and the \lq\lq short form'')
      so that they can be = used separately.
\item Occasionally, two different schemes may be used = in parallel
      within the same = document. (For example, in \cite{norusis},
      a software-house seems = to use \lq\lq short form'' when citing
      its own publications, = but author-date when citing other publications.)
\end{itemize}
Thus, it seems to me that the three schemes are best = regarded as logically
distinct.

However, within a particular scheme, there are = variations of punctuation, etc.,
that can be regarded as matters of \lq\lq house = style''.
For example, some journals that have adopted a \lq\lq = reference by number''
scheme use bracketed numerals for citations, while = others use superscripts.
Such variations can be accomodated by differences = between style files.

\subsection{Additional references}
\label{support-additional}

In addition to a list of \lq\lq works cited'', some = documents
have an additional reference-list that specifies = \lq\lq further reading''
or \lq\lq all sources consulted'' (see \cite[pp.\ 182 = \& 192]{butcher},
\cite[p.\ 40]{huth} and \cite[p.\ = 22]{bs-4821}).  There needs to be some
provision for typesetting such additional = lists.


\section{Deficiencies in \LaTeX\ 2.09}
\label{2.09-problems}

\subsection{Citations}
\label{2.09-citations}

When used in conjunction with \BibTeX\ and = \verb+\bibliographystyle{unsrt}+,
\LaTeX\ 2.09 makes a good job of organising citations = (and sorting the
corresponding reference-list) according to the \lq\lq = reference by number''
scheme as required by many journals.

Generally, however, \LaTeX\ 2.09 does not provide the = breadth or depth
of facilities needed to support the variety of = requirements for
mainstream publishing:
\begin{itemize}
\item It is unfortunate that the \lq\lq reference by = number'' sequence obtained
      most naturally by the = do-it-yourself-er \cite[p.\ 73]{lamport} from
      \LaTeX\ 2.09 (\lq\lq = order of appearance within {\tt thebibliography}'')
      is unlikely to be what = the do-it-yourself-er's journal-editor requires
      (which will usually be = \lq\lq order of first citation'').  The
      do-it-yourself-er is = given no warning (either in \cite{lamport} or by
      the software) that = sorting is likely to be needed.
\item Although one can use style-options such as {\tt = apalike} and
      {\tt aaai} to = re-define \verb+\cite+ and {\tt thebibliography}
      for an author-date = scheme, there are many obstacles placed in the
      user's way:
      \begin{itemize}
      \item The existence of = the style-options is not documented in
          &nbs= p; \cite{lamport}.
      \item If one finds a = style-option  in a (software) archive, it
          &nbs= p; may need modification to produce the precise effect required.
      \item It is not = obvious how one should refer separately to two
          &nbs= p; items (author and date) supplied via a \verb+\bibitem+ = argument
          &nbs= p; originally designed for one.  The do-it-yourself-er might
          &nbs= p; have to study style files such as {\tt aaai.sty} and {\tt bbl}
          &nbs= p; files such as those produced by {\tt aaai-named.bst} to
          &nbs= p; deduce how to do this.
      \end{itemize}
\item The \lq\lq short form'' scheme seems = unsupported.
\item At certain points in a document, an author my = need to cite
      several works at = once.  It may be necessary to specify a
      page (or section, = etc\@.) for each work.  For instance,
      \cite[p.\ = 404]{chicago} suggests references of the form
      \lq\lq (Kelley 1896a, = 10; Kelley 1896b; Kelley 1907, 3)''.
      This is not easy in = \LaTeX\ 2.09, since \verb+\cite+'s
      optional argument = applies to the citation as a whole.  The
      author cannot supply a = separate \lq\lq optional argument''
      for each work.  = (By contrast, {\sf EndNote}'s analogous facilities
      \cite[p.\ 58]{endnote} = seem to allow each individual work
      to be given its own = \lq\lq additional text''.)
\item It does not seem easy to use different schemes = in parallel
      within the same = document.  If \verb+\cite+ and
      {\tt thebibliography} = are defined as required for one scheme,
      they will usually be = unsuitable for any other.
\end{itemize}

\subsection{Additional references}
\label{2.09-additional}

As stated in section \ref{support-additional} an = author may need to
typeset a list of \lq\lq further reading'' etc., in = addition to
the usual list of \lq\lq works cited''.

If using the {\tt thebibliography} environment from = one of \LaTeX\
2.09's standard styles for such additional = references, an author will be
faced with the following problems:
\begin{itemize}
\item the title will be the same as that for the list = of \lq\lq works
      cited'', namely \lq\lq = References'' for {\tt article} and
      \lq\lq Bibliography'' = for {\tt report} and {\tt book}
\item the \lq\lq labels'' (which may be appropriate = in the list
      of \lq\lq works = cited'', particularly for the \lq\lq reference
      by number'' scheme) = will also appear in the
      additional list (where = they are inappropriate), because
      both lists use the = same definition of \verb+\bibitem+
\item by default, the \lq\lq labels'' will not be = unique, since
      the \lq\lq works = cited'' list and the \lq\lq additional references''
      list will both be = numbered from one
\item it will be necessary to supply dummy {\it = cite-key\/}s,
      purely to satisfy the = syntax required for a \verb+\bibitem+.
\end{itemize}

\subsection{Other problems}
\label{2.09-other}

The definitions of the {\tt thebibliography} = environment in \LaTeX\
2.09's standard styles:
\begin{itemize}
\item issue either a \verb+\section*+ or a = \verb+\chapter*+ command,
      using a {\it heading} = of \lq\lq References'' for {\tt article}
      and \lq\lq = Bibliography'' for {\tt report} and {\tt book}
\item set {\it left-head\/} and {\it right-head\/} to = either
      \lq\lq REFERENCES'' or = \lq\lq BIBLIOGRAPHY''
\item do not arrange for a table-of-contents = entry.
\end{itemize}
These definitions can cause problems when the {\it = heading}, etc.\
supplied by the standard style is inappropriate, or = when a table-of-contents
entry is desired.
Admittedly, anyone who doesn't like the standard = styles is free to
take copies of the style files and modify them to = suit their requirements.
However, I have the impression that:
\begin{itemize}
\item among people who are competent to modify style = files,
      modification of these = aspects of the standard styles is \lq\lq the
      rule'' rather than = \lq\lq the exception''
\item those \LaTeX\ users who aren't particularly = computer-literate
      find the whole = business mysterious, and seek out support staff
      who have to modify = these aspects of the style files for them.
\end{itemize}
Overall, this seems to be an area where \LaTeX\ 2.09 = is failing to
\lq\lq free people from formatting concerns to allow = them to
concentrate on writing'' \cite[p.\ = 8]{lamport}.

An associated problem is that modified style files may = no longer be
compatible with standard utilities such as {\tt = lablst}.

\section{Introduction of new facilities}
\label{new-facils}

It has been decided \cite{mittelbach} that \LaTeX\ 3.0 = will be compatible with
\LaTeX\ 2.09 input files.  Thus, in particular, = \LaTeX\ 3.0 must define
\verb+\cite+ and \verb+thebibliography+ so that they = have the same effect on
\LaTeX\ 2.09 input files as the \LaTeX\ 2.09 = definitions do.  This implies that
it would be difficult for \LaTeX\ 3.0 to (for = example) define \verb+\cite+
so that there can be an optional argument for each = work in a multiple citation
and define \verb+\bibitem+ so that it can have an = \lq\lq author'' argument and
a \lq\lq date'' argument.

It therefore seems best to provide duplicates of the = \LaTeX\ 2.09 facilities
in \LaTeX\ 3.0 (for \lq\lq backwards compatibility'') = but to attempt to
provide new commands/environments in parallel so as = to provide the required
functionality.  The new facilities would be = regarded as the \lq\lq normal''
facilities, would be described in the body of the = successor to \cite{lamport},
 and
would be the natural choice for new users.  The = old facilities would be
regarded as \lq\lq deprecated'' and relegated to an = appendix of the successor
to \cite{lamport}.

Thus we can have both backwards compatibility and = improved facilities
for the future.

\section{Division of labour}
\label{div-of-labour}

\subsection{Details needed for document \lq\lq as a = whole''}

The three basic citation schemes mentioned in section = \ref{basic-schemes}
determine certain details of a document \lq\lq as a = whole''.  For each
citation, there must be an entry in a = reference-list.  Each entry in
the relevant reference-list must have associated = information that can be
used in citations.

\subsection{Details needed for reference-list, = etc.}

There are a lot of other details that need to be = resolved.

The information within each reference-list entry will = probably need
formatting according to certain rules of \lq\lq house = style''.
The information given in citations needs organising = in a consistent way
(particularly for the \lq\lq short form'' = scheme).

Different people may want to assemble their = reference-lists in different ways.
Some people may wish to \lq\lq do it themselves'' = \cite[p.\ 73]{lamport} from
a physical card-index, while some may prefer to use = \BibTeX\ to get details
>from a {\tt bib} file.  In some disciplines, = proprietary systems such as
{\tt EndNote} \cite{endnote} seem popular (because = they help the user to search
a database for literature to cite, as well as helping = the user
incorporate details of the literature into a = document).
Researchers may also wish to incorporate material = obtained by searching
details held on a {\sc cd-rom}.

A reference-list generally needs sorting into a = particular order.  Since the
list may occupy several pages, I assume that any = sorting is best done outside
\LaTeX, either by other software (e.g., \BibTeX) or = manually by the author.

\subsection{\LaTeX\ and other software}

It seems best to regard the movement of text-strings = (e.g., an author's
surname) within the \lq\lq document as a whole'' as a = task that is distinct
>from the arrangement of details within the = text-strings, and to assume a
\lq\lq division of labour'' in which the former task = is performed by \LaTeX\
while the latter is performed by some other software = or manually by the author.
The \lq\lq division of labour'' between \LaTeX\ 2.09 = and \BibTeX\ seems to set
a good precedent.

This division of labour will lead to modular = software.  Once the
interface between a reference-list and the rest of = the document has
been defined, people can use \LaTeX\ for the body of = their document,
but can:
\begin{itemize}
\item experiment with different software (\BibTeX, = {\sf EndNote})
      for formatting the = details of their reference-lists
\item enhance the other software (e.g., \BibTeX) = independently
      of enhancements to = \LaTeX.
\item lay their reference-lists out manually if they = prefer.
\end{itemize}

\section{\protect\LaTeX\ 3.0: A possible user = interface?}
\label{what-to-do}

\subsection{Specifications and names}

If the reasoning given in sections \ref{conventions}, = \ref{new-facils}
and \ref{div-of-labour} is accepted, consideration = needs to be given to
the form that new commands/environments should take = in order to support the
three basic citation schemes, and to provide = facilities for \lq\lq additional
references''.  In particular, it will be = necessary to choose
names other than \verb+\cite+, {\tt thebibliography} = and \verb+\bibitem+ (since
these names will be kept for the facilities provided = for compatibility with
\LaTeX\ 2.09).


\subsection{Four sets of commands/environments}
\label{4-sets}

It seems to me that it would probably be convenient to = have three sets of
commands/environments for dealing with citations and = the corresponding
reference-lists, each set specifically designed to = implement a particular
citation scheme.  Having three such sets gives = scope for taking proper
account of the peculiarities of each scheme, without = having one scheme
adversely affected by the peculiarities of = another.

To avoid the difficulties mentioned in section = \ref{2.09-additional},
it might also be worth having a specific environment = for
\lq\lq additional references''.

\LaTeX\ 3.0 might, for example, have = commands/environments as specified
in the following table.

\begin{center}
\begin{footnotesize}
\renewcommand{\arraystretch}{1.25}
\begin{tabular}{lccccccc}
\hline
          &nbs= p;         &  = Citation        & Environment for = & Entry = in           \\
          &nbs= p;         = &           &n= bsp;      & reference-list  & = reference-list     \\
\hline
Reference by number &  \verb+\numcite+ & = {\tt numrefs}   & \verb+\numentry+
 \\
\hline
Author-date         = &  \verb+\dcite+
          &nbs= p;            = ;            =     & {\tt adrefs}    & = \verb+\adentry+    \\
          &nbs= p;         &  = \verb+\adcite+ = &           &n= bsp;     = &           &n= bsp;     \\
\hline
Short = form          &  = \verb+\firstcite+  & {\tt sfrefs}    & = \verb+\sfentry+
  \\
          &nbs= p;         &  = \verb+\sfcite+&         =      = &           &n= bsp;         \\
\hline
Additional references&    = ---         &  {\tt = morerefs} & \verb+\moreentry+ \\
\hline
{\it Analogue at 2.09} &  \verb+\cite+ & = {\tt thebibliography}
          &nbs= p;            = ;            =             &= nbsp;          & = \verb+\bibitem+   \\
\hline
\end{tabular}
\end{footnotesize}
\end{center}

Here it is assumed that:
\begin{itemize}
\item \verb+\numcite+ and \verb+\numentry+ have {\it = key-list} and
      {\it cite-key} = (respectively) as their only mandatory arguments.
\item \verb+\dcite+ and \verb+\adcite+ have {\it = key-list} as argument.
      \verb+\dcite+ gives a = citation of the form (1972),
      while \verb+\adcite+ = gives a citation of the form (Crane, 1972).
      \verb+\adentry+ has = three arguments: the {\it cite-key},
      the author (e.g., = Crane), and the date (e.g., 1972).
\item \verb+\firstcite+ and \verb+\sfcite+ have {\it = key-list} as argument.
      \verb+\firstcite+ = gives the form of citation to be used when a work
      is first = mentioned.  \verb+\sfcite+ gives the short form
      to be used in = subsequent citations.
      \verb+\sfentry+ might = have 3 arguments: the {\it cite-key}, the form
      of reference to be = used at the first citation, and the short form
      to be used = subsequently.
\end{itemize}

Although it would be desirable for the successors to = the ``standard styles''
to define facilities for all three citation schemes, = other
\verb+\documentstyle+s need not define facilities for = all three.  For example,
a journal that wants its authors to use the = author-date scheme would supply a
style file that only provides author-date = facilities.

\subsection{Further details}
\label{further-details}

\subsubsection{Reference by number}

The \verb+\numcite+ and \verb+\numentry+ commands = might take the form
\verb+\numcite{+{\it key-list}\verb+}+ and
\verb+\numentry{+{\it cite-key}\verb+}+.  Notice = that, since \verb+\numentry+
is specifically designed for \lq\lq reference by = number'', there is no need to
allow an optional {\it label} argument like that for = \verb+\bibitem+.

To conform to the ISO specification \cite{iso-690}, = the successors to the
``standard styles'' would arrange for \verb+\numcite+ = to give a citation of the
 form (24)
and for \verb+\numentry+ to give a reference-list = entry of the form
\begin{description}
\item[{\rm 24.}] {\sc Crane, D.} {\it Invisible = colleges.} \dots
\end{description}

Perhaps \LaTeX\ 3.0 could use the {\tt aux} file to = refine an initial estimate
of the width of the final \verb+\numentry+'s \lq\lq = label'', so that the
do-it-yourself-er wouldn't need to supply a {\it = widest-label\/} argument.

\subsubsection{Author-date}

The commands \verb+\dcite+, \verb+\adcite+ and = \verb+\adentry+ might
be defined to have the forms \verb+\dcite{+{\it = key-list}\verb+}+,
\verb+\adcite{+{\it key-list}\verb+}+ and
\verb+\adentry{+{\it cite-key}\verb+}{+{\it = author}\verb+}{+{\it date}\verb+}+.
The {\tt adrefs} environment would {\it not} have a = {\it widest-label}
argument, since in this scheme entries in the = reference-list are unlabelled.

If such a definition of \verb+\adentry+ was documented = in the successor to
\cite{lamport}, a do-it-yourself-er would be able to = use the author-date
system just as easily as the \lq\lq reference by = number'' system.

To conform to the ISO specification \cite{iso-690}, = the successors to the
``standard styles'' would arrange for \verb+\dcite+ = to give a citation of
the form (1972), for \verb+\adcite+ to give a = citation of the form
(Crane, 1972), and for \verb+\adentry+ to give a = reference-list entry with no
label.

\subsubsection{Short form}

The \verb+\firstcite+, \verb+\sfcite+ and = \verb+\sfentry+ commands might
be defined as \verb+\firstcite{+{\it = key-list}\verb+}+,
\verb+\sfcite{+{\it key-list}\verb+}+ and
\verb+\sfentry{+{\it cite-key}\verb+}[+{\it
      = fairly-full-form}\verb+]{+{\it short-form}\verb+}+.
Such  definitions would, in effect, automate = Butcher's manual method of
ensuring consistency \cite[p.\ 178]{butcher}.  = Since, in some situations, a
reference is given in full when it is first cited = \cite[p.\ 407]{chicago},
the default {\it fairly-full-form} would be the full = reference  as
put in the reference-list by \verb+\sfentry+.
The {\tt sfrefs} environment would {\em not} have a = {\it widest-label}
argument.

The successors to the ``standard styles'' would = arrange for \verb+\firstcite+
to produce the {\it fairly-full-form} and = \verb+\sfcite+ to produce the
{\it short-form}.%
\footnote{%
This makes the pessimistic assumption that \LaTeX\ = can not itself determine
whether a citation is the \lq\lq first citation'' of = a particular work.
If someone was ingenious enough to produce code that = determined whether a
citation is a \lq\lq first citation'', = {\tt\ttbackslash firstcite} would be
unnecessary (except, perhaps, for the construction of = tables of abbreviations
\cite[p.\ 414]{chicago}.)%
}
To conform to the ISO specification \cite{iso-690}, = neither
\verb+\firstcite+ nor \verb+\sfcite+
would add any punctuation (but, for example, a style = file that implemented
the MLA conventions would have to add brackets = \cite[ch.\ 5]{gibaldi}).
In the successors to the ``standard styles'',
the \verb+\sfentry+ would produce an entry with no = label.

People producing other style files would be free to = implement other
conventions \cite[p.\ 168]{butcher}.

Some works may have no bibliography or may have just a = \lq\lq select
bibliography'' \cite[p.\ 168]{butcher}.  For = such works, it will still
be necessary to supply the details for use by = \verb+\firstcite+ and
\verb+\sfcite+.  It may therefore be worth = allowing a form of
{\tt sfrefs} (e.g., = \verb+\begin{sfrefs}[null]+)
that holds details of cited works but does no = typesetting.

\subsubsection{Additional references}
\label{3.0-additional}

Since the entries in an \lq\lq additional list'' will = not be cited as such
(although an \lq\lq all sources consulted'' list may = contain a duplicate of
a cited entry in a \lq\lq works cited'' list), the = list will be typeset
without \lq\lq labels''.  Even in a document = that uses the \lq\lq reference by
number'' citation scheme (and so needs \lq\lq = labels'' in the {\tt numrefs}
list), there will be no \lq\lq labels'' for the = entries in an additional list.

It therefore seems likely that the {\tt morerefs} = environment could
be implemented as a variation of {\tt adrefs} or {\tt = sfrefs}, the main changes
being:
\begin{itemize}
\item a change of title (but see section = \ref{reflist-scope})
\item absence of
      {\it cite-key, author, = date, fairly-full-form} and {\it short-form}
      arguments.
\end{itemize}

\subsection{Order within the reference-list}

As stated in section \ref{div-of-labour}, it is = probably best to leave
any sorting of the reference-list to some other = software, or to the author.

However, it might be possible for \LaTeX\ to provide a = warning if a
reference-list is obviously in the wrong order.  = Perhaps:
\begin{itemize}
\item although there may be no easy alternative to = numbering
      \verb+\numcite+s in = order of appearance within {\tt numrefs}
      (even though \lq\lq = order of first citation'' is usually what
      is required), \LaTeX\ = could give a warning if a \verb+\numcite+
      gave a number that = exceeded the \lq\lq biggest number produced
      by \verb+\numcite+ so = far'' by more than one.
\item there could be a warning if an \verb+\adentry+ = had an
      {\it author} whose = first letter came before the first letter of the
      preceding = \verb+\adentry+'s {\it author} in the alphabet.
\end{itemize}

\subsection{Citation of a specific division}
\label{division}

As stated in section \ref{2.09-citations}, provision = needs to be made for
the citation of a particular division (e.g., page, = section, chapter,
equation) of another work.  The syntax of = citation commands should
not only allow several works to be cited = simultaneously, but should also
allow the relevant division of each work to be = specified.

>From the author's point-of-view, there would be a = variety of satisfactory
ways to specify citations that are to appear = as
``[4, p.\ 10; 5; 6, p.\ 3]'', e.g.
\begin{verbatim}
    \numcite{smith[p. = 10],brown,jones[p. 3]}
    \numcite{smith, p. 10; brown; = jones, p. 3}
    \numcite{smith & p. 10; brown; = jones & p. 3}
\end{verbatim}
The precise syntax would have to take
account of the practicalities of programming a = command that has to be able
to accept pairs of arguments, where the second member = of each pair is optional.

Analogous facilities would be needed for author-date = and \lq\lq short form''
citations.

Incidentally, since abbreviations such as p., ch., = sec., and fig.\ are
common when such divisions are specified, I think = that citation commands
should arrange for the optional arguments to be = typeset with
\verb+\frenchspacing+.

\section{Details of reference-lists}

\subsection{Variations within mainstream publishing = practice}
\label{mainstream-lists}

Although many academic and technical publications = involve only a single
undivided reference-list, some such publications = involve:
\begin{description}
\item[more than one list]
      This situation can = arise:
      \begin{itemize}
      \item when there is a = list of \lq\lq further reading'' etc.,
          &nbs= p; as well as the list of \lq\lq works cited''.
          &nbs= p; This case has been covered in sections = \ref{support-additional},
          &nbs= p; \ref{2.09-additional}, \ref{4-sets} and \ref{3.0-additional}.
      \item when conference = proceedings are produced, since each
          &nbs= p; contribution may have its own reference-list.
      \item in manuals for = software.  For example, in \cite{norusis}, a
          &nbs= p; software house's own publications are introduced in the = preface
          &nbs= p; and cited (in effect) using a \lq\lq short form'' scheme, = while
          &nbs= p; other people's publications are listed at the end of the = manual
          &nbs= p; and are cited using the author-date scheme.
      \end{itemize}
\item[subdivisions within a list]
      Some reference-lists, = particularly in the humanities, are subdivided
      according to the = source of the cited documents (see
      \cite[p.\ = 183]{butcher}, \cite[p.\ 425]{chicago} and
      \cite[p.\ = 88]{gibaldi}).
\end{description}

In some cases, an author may wish to add explanatory = paragraphs describing,
for example, how material was chosen for a \lq\lq = select bibliography''
\cite[fig.\ 15.11]{chicago} or information about = access to (document)
archives \cite[fig.\ 15.16]{chicago}.

\subsection{\protect\LaTeX\ 2.09}

\LaTeX\ 2.09 can cope with documents that have more = than one
{\tt thebibliography} environment, and seems to deal = satisfactorily
with a situation in which some \verb+\cite+ commands = are to
one {\tt thebibliography} and some are to another = (provided that
the {\it cite-key\/}s are unique).  The default = effect is
to give {\it label\/}s that are not unique, which = will be acceptable
when each contribution to a \lq\lq conference = proceedings'' has its
references numbered from one, but not if \lq\lq works = cited''
and \lq\lq additional references'' are both numbered = from one
(see section \ref{2.09-additional}).

The specification of {\tt thebibliography} \cite[p.\ = 187]{lamport}
does not allow anything other than \verb+\bibitem+s = within a
{\tt thebibliography} environment.  Hence, it is = not clear
how one can introduce subheadings within a = reference-list.
(In practice, a \verb+\section*+ seems to work = between
\verb+\bibitem+s, but I suspect that it puts \LaTeX\ = 2.09 into a loop
if placed before the first \verb+\bibitem+.)

Anyone trying to add explanatory paragraphs (as in = \cite[fig.\ 15.11]{chicago}
and \cite[fig.\ 15.16]{chicago}) will probably find = that \LaTeX\ 2.09
objects that \lq\lq{\verb+Something's wrong--perhaps = a missing \item+}''.

\subsection{\protect\LaTeX\ 3.0}

Ideally, in order to provide support for the = conventions that are routine
in mainstream publishing practice, \LaTeX\ 3.0 should = be able to cope with
all the variations outlined in section = \ref{mainstream-lists}.

\subsubsection{Multiple lists}

The suggestions made in section \ref{what-to-do} would = probably cater for most
situations where a document has more than one = reference-list.

The distinction between {\tt morerefs} and the other = environments for
reference-lists would take care of situations where = there is a list of
\lq\lq additional references'' as well as a list of = \lq\lq works cited''.
The distinction between the \lq\lq short form'' = commands/environment
and the other commands/environments would take care = of situations where a
software house uses \lq\lq short form'' for its own = publications
and some other scheme for other publications.  = Conference proceedings
will be able to have \lq\lq a reference-list for each = contribution''
if \LaTeX\ 3.0 follows the \LaTeX\ 2.09 precedent = that allows
more than one {\tt thebibliography} in a = document.

\subsubsection{Subdivisions and explanatory = paragraphs}

I have the impression that, because the sciences have = different conventions
>from the humanities, people using the \lq\lq = reference by number'' citation
scheme are unlikely to want the options of = subdividing their reference-list
and inserting explanatory paragraphs.  = Therefore, it would be legitimate to
say (for example) \lq\lq subdivisions and explanatory = paragraphs are supported
within {\tt adrefs}, {\tt sfrefs} and {\tt morerefs} = but not within
{\tt numrefs}'', if this made the programming task = easier.

For example, it might be convenient to implement {\tt = numrefs} as
a \lq\lq list-making environment'' (as in \LaTeX\ = 2.09) but to implement
the other environments in some other way.  Lack = of support for subdivisions
and explanatory paragraphs is unlikely to matter in = {\tt numrefs}; the
\lq\lq other way'' (more like \verb+\paragraph+, = perhaps?) might make it
easier to implement support for these facilities in = the other environments.

\subsubsection{Other problems}
\label{reflist-scope}

One approach to some of the problems mentioned in = section \ref{2.09-other}
is for the standard styles to define the heading for = the reference-list by,
for example, \verb+\def\numrefsheading{References}+, = so that anyone who wants
to change the heading can do so by issuing a = \verb+\renewcommand+ command
somewhere before the start of their = reference-list.

Another approach is to work in terms of the standard = publishing industry
concept of \lq\lq back matter'' \cite[p.\ = 4]{chicago}.  Instead of having to
understand where the {\it heading}, {\it left-head}, = {\it right-head} and
table-of-contents entry (or lack of it) originate for = units such as the
glossary (if any), the reference-list(s) and the = index (if any)
{\em separately}, an author would only have to = understand how these features
are treated {\em consistently} within \lq\lq back = matter''.

Although the \lq\lq back matter'' approach could be = used if environments
such as {\tt numrefs} followed the {\tt = thebibliography} precedent and issued
commands such as \verb+\chapter+ or \verb+\section+ = themselves, authors
might find the way that {\it heading}, {\it = left-head}, {\it right-head} and
table-of-contents entry materialize less mysterious = if it was just the same
for a reference-list as for (say) a glossary.  = This would imply that
{\tt numrefs}, {\tt adrefs}, {\tt sfrefs} and {\tt = morerefs} should
not issue commands like \verb+\chapter+ or = \verb+\section+ themselves.
As a bonus, it would then be possible for an author = to insert an explanatory
paragraph before the reference-list, and to arrange = for subdivisions.

For example, if there was a {\tt backmatter} = environment within which
\verb+\chapter+ was treated as defining a unit of = \lq\lq back matter'',
an author's file might contain commands such = as
\begin{verbatim}
\begin{backmatter}
   \chapter{Glossary}
      ...
   \chapter{References}
      \section{Primary = sources}
      \begin{sfrefs}
      ...
      \end{sfrefs}
      \section{Secondary = sources}
      \begin{sfrefs}
      ...
      \end{sfrefs}
   \chapter{Further reading}
      = \begin{morerefs}
      ...
      \end{morerefs}
\end{backmatter}
\end{verbatim}

\section{Conclusion}

\LaTeX\ has a large number of users, and potential = users, who wish to produce
documents that conform to the conventions that are = standard in academic
publishing.  One element of their requirement is = the need to conform to the
conventions for citations and reference-lists that = are usual in their
disciplines.

The choice for \LaTeX\ 3.0 may be between:
\begin{enumerate}
\item having more facilities for citations and = reference-lists than
      \LaTeX\ 2.09, perhaps = as suggested in section \ref{what-to-do}.
      This would imply an = increase in:
      \begin{itemize}
      \item the amount of = code needed to implement the facilities, and
          &nbs= p; the guru time needed for writing the code
      \item the number of = pages needed, in the successor to \cite{lamport},
          &nbs= p; to describe the facilities --- perhaps 8 pages rather than
          &nbs= p; the 2 pages in \cite{lamport}.
      \end{itemize}
\item no significant increase in the facilities = provided for citations
      and = reference-lists.  Contrary to the idea of \lq\lq freeing = people
      from formatting = concerns to allow them to concentrate on writing''
      \cite[p.\ 8]{lamport}, = many authors (perhaps most authors) would be
      wasting time:
      \begin{itemize}
      \item hacking at = style-files
      \item searching = (software) archives for ready made solutions
      \item taking up = support staff's time in the search for advice (with the
 support staff
          &nbs= p; in turn taking up gurus' time in their search for solutions).
      \end{itemize}
      Moreover, most of this = time would be wasted by (or on behalf of) authors
      who don't want = anything at all exotic; they just want to conform
      to the conventions = that are standard in traditional academic publishing.
\end{enumerate}
I'm inclined to think that the first option would be = the lesser of the
two evils.

\section*{Appendix: Interface with = \protect\BibTeX}
\addcontentsline{toc}{section}{Appendix: Interface = with \protect\BibTeX}

The preceding sections make some suggestions for a = \LaTeX\ 3.0 user
interface that would enable the do-it-yourself-er to = conform to
the conventions that are usual in academic = publishing.
It is also necessary to consider the implications for = the interface to
\BibTeX.

\subsection*{Single reference-list}

Inspecting {\tt bst} files gives me the impression = that, if it
was decided to adopt a scheme such as that described = in section
\ref{what-to-do}, it would be fairly easy to produce = new {\tt bst} files
to supersede existing ones.  For example, a {\tt = bst} file
that implemented a \lq\lq reference by number'' = scheme would write
\verb+\numentry+ commands rather than \verb+\bibitem+ = commands.

If {\tt bst} files were created in this way, they = would be able to
deal with the straightforward situation when there is = a single
reference-list that contains all works cited (plus, = possibly,
any works specified by a command like = \verb+\nocite+).

\subsection*{Multiple reference-lists, all with the = same style}

More complicated situations can arise in which a = document involves
several reference-lists.  For example:
\begin{itemize}
\item The editor of the proceedings of a conference = might want the
      published proceedings = to have a reference-list at the end of each
      chapter.
\item If, as suggested in section = \ref{reflist-scope}, {\tt sfrefs} was
      implemented in a way = that allowed a sequence of {\tt sfrefs} environments
      to each be preceded by = a \verb+\section+ command, then, as far as
      \BibTeX\ is concerned, = each {\tt sfrefs} environment might be a separate
      reference-list.
\end{itemize}

In both these examples, the document would involve = several reference-lists,
but each reference-list would need to be typeset in a = common style.
I assume that the main problems would be in = arranging:
\begin{itemize}
\item to have multiple {\tt bbl} files, or distinct = divisions of a single
      {\tt bbl} file
\item that each reference-list takes its entries from = the correct {\tt bbl}
      file, or from the = correct division of a single {\tt bbl} file.
\end{itemize}

\subsection*{Two reference-lists, each with a = different style}

People producing documents that have a second = reference-list (e.g.,
\lq\lq further reading'') in addition to the list of = \lq\lq works cited''
might want the first list typeset in one style and = the second
list typeset in another.  (In particular, if the = \lq\lq reference by number''
scheme is used, the first list will have \lq\lq = labels'' but the second
list will have no \lq\lq labels''.)  If the = commands/environments suggested
in section \ref{what-to-do} were implemented, the = first list would use
{\tt numrefs}, {\tt adrefs} or {\tt sfrefs}, while = the second list would
use {\tt morerefs}.

In this situation, it would be necessary to = communicate to \BibTeX\
that two lists are required, but that they are to be = typeset in different
styles.  Since the second list is to contain = \lq\lq works {\em not\/}
cited'', it will also be necessary to specify the = works to be shown in the
second list.

If it is decided to extend the interface between = \LaTeX\ and \BibTeX\ to
cater for such situations, it will probably be = necessary to consider
defining alternatives to \LaTeX\ 2.09's = \verb+\bibliography+ and
\verb+\bibliographystyle+ commands, since it seems = unlikely that the syntax
of the \LaTeX\ 2.09 commands could be extended so as = to pass the necessary
information.  One might, for example, consider = syntax such as
\verb+\bibtexcites[+{\it cites-style}\verb+]{+{\it = bib-files}\verb+}+
and
\verb+\bibtexmore[+{\it more-style}\verb+]{+{\it = bib-files}\verb+}{+{\it
      = key-list}\verb+}+.
Here, it is assumed that:
\begin{itemize}
\item the \verb+\documentstyle+ would set defaults = for the {\it cites-style}
      and {\it more-style} = that are to be passed to \BibTeX, but the user
      can over-ride the = defaults via the optional arguments to
      \verb+\bibtexcites+ = and \verb+\bibtexmore+
\item \verb+\bibtexmore+'s {\it key-list} argument = would be used to
      specify the works to = be included in the list of \lq\lq additional
      references''.
\end{itemize}

If it is not practicable to extend the \LaTeX/\BibTeX\ = interface to cater for
these situations automatically, it would presumably = be a matter of
some \lq\lq human intervention'':
\begin{itemize}
\item to prepare a {\tt bbl} file for the \lq\lq = additional references''
\item to \verb+\input+ the {\tt bbl} file.
\end{itemize}

\begin{thebibliography}{00}
\bibitem{lamport} {\sc Leslie Lamport.}
      {\it \itlatex: A = document preparation system.}
      Addison-Wesley, = 1986.
\bibitem{mittelbach} {\sc Frank Mittelbach and Rainer = Sch\"{o}pf.}
      With \LaTeX\ into the = ninties.
      {\it = TUGboat,}   1989, {\bf 10}, 681--690.
\bibitem{bs-5605}
      {\it Citing = publications by bibliographical references.}
      BS 5605.  British = Standards Institution, 1978.
\bibitem{bs-6371}
      {\it Citation of = unpublished documents.}
      BS 6371.  British = Standards Institution, 1983.
\bibitem{butcher}
      {\sc Judith = Butcher.}
      {\it = Copy-editing.}
      Cambridge University = Press, 1981.
\bibitem{chicago}
      {\it The Chicago = manual of style.}
      Chicago University = Press, 1982.
\bibitem{gibaldi}
      {\sc Joseph Gibaldi = and Walter S. Achert.}
      {\it MLA handbook for = writers of research papers.}
      Modern Language = Association of America, 1988.
\bibitem{huth}
      {\sc Edward J. = Huth.}
      {\it Medical style and = format.}
      ISI Press, = 1987.
\bibitem{inter}
      {\sc International = Committee of Medical Journal Editors.}
      Uniform requirements = for manuscripts submitted to biomedical
          &nbs= p; journals.
      {\it British Medical = Journal,}   1988, {\bf 296}, 401--405.
\bibitem{iso-690}
      {\it Documentation --- = bibliographic references
          &nbs= p; --- content, form and structure.}
      ISO 690.  = International Organization for Standardization, 1987.
\bibitem{oconnor}
      {\sc Maeve = O'Connor.}
      {\it Editing = scientific books and journals.}
      Pitman Medical, = 1978.
\bibitem{page}
      {\sc Gillian Page, = Robert Campbell and Jack Meadows.}
      {\it Journal = publishing: principles and practice.}
      Butterworths, = 1987.
\bibitem{norusis}
      {\sc Marija J. = Noru\v{s}is.}
      {\it SPSS-X = Introductory Statistics Guide for Release^3.}
      SPSS Inc., = 1988.
\bibitem{bs-4821}
      {\it Presentation of = theses and dissertations.}
      BS 4821.  British = Standards Institution, 1990.
\bibitem{endnote}
      {\it EndNote:  A = reference database and bibliography maker.}
      Berkeley: Niles \& = Associates, Inc., 1989.
\end{thebibliography}

\end{document}


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