Formatting Information

5.3.2.1 Choosing between BIBTEX and biblatex

LATEX has two systems for doing citations and references, BIBTEX (old) and biblatex (new): both of them use the same file format, also called BIBTEX. Both support the four common ways of indicating a citation: author-year, numeric, abbreviated alphabetic, and footnoted; plus a wide range of others.

BIBTEX

the older BIBTEX has been in use for many decades and is still specified in some publishers’ document classes, especially for journal articles and books, and particularly those which have not been updated for a long time. While it will continue to work, it has several drawbacks:

1. it doesn’t handle non-ASCII characters easily, so accents and non-Latin words are a problem;

2. the same applies to the sort-and-extract program it uses (also called bibtex)

3. the style format files (.bst files) are written in BIBTEX’s own rather strange, unique, and largely undocumented language, making it extremely difficult to modify them or write new ones;

4. many of the style format files are now very old and out of date;

5. the range of data fields in references is limited and also out of date.

biblatex

the newer biblatex system is now a well-established LATEX package to replace almost all of old BIBTEX. The main advantages are:

1. it uses the same .bib files as for old BIBTEX, but lets you use many new document types and data field names.

2. it works with UTF-8, so non-ASCII, non-Latin, and other writing systems are handled natively when using XƎLATEX or LuaLATEX.

3. there is a new sort-and-extract program (biber) to replace bibtex, which also handles UTF-8 natively.

4. the style format files are written entirely in LATEX syntax, and are under active development, so updating or writing layout formats it is much easier than with BIBTEX.

5. it supports the four popular citation formats listed above natively, without the need for additional packages.

The only current drawback is that there are still a few uncommon and less-used reference formats that are still only supported in BIBTEX and not yet available in biblatex. If you are required to use one of these, you are going to be stuck with BIBTEX (unless you’d like to write a new biblatex add-on to handle it).

The biblatex package with the biber program is therefore recommended, especially with XƎLATEX or LuaLATEX. From here on, I shall be concentrating on biblatex.

5.3.2.2 The BIBTEX file format

The same file format for BIBTEX files is used for both BIBTEX and biblatex, regardless of whether you use biber or bibtex, so if you have existing BIBTEX files, they will continue to work, but it’s a good idea to update old files with some of the more accurate field names provided by biblatex.

The file format is specified in the original BIBTEX documentation (look on your system for the file btxdoc.pdf). The biblatex package and its updated style formats provide many more fields and document types than we can describe here.

Each BIBTEX entry starts with an @ sign and the type of document (eg @article, @book, etc), followed by the whole entry in a single set of curly braces. The first value MUST be a unique BIBTEX key (label) that you make up, which you will use to cite the reference with; followed by a comma:

@book{fg, ... }

Then comes each field (in any order), using the format:

fieldname = {value},

There MUST be a comma after each line of an entry except the last line:

@book{fg,
  title     = {{An Innkeeper’s Diary}}, 
  author    = {John Fothergill}, 
  edition   = 3, 
  publisher = {Penguin}, 
  year      = 1929, 
  address   = {London} 
}

Some TEX-sensitive editors have a BIBTEX mode which understands these entries and provides menus, templates, and syntax colouring for writing them. The rules are:

• There MUST be a comma after each line of an entry except the last line;

• There MUST NOT be a comma after the last field in the entry (only — eg after {London} in the example)

• Some styles recapitalise the title when they format: to prevent this, enclose the title in double curly braces as in the example;

• You MUST use extra curly braces to enclose multi-word surnames, otherwise only the last will be used in the sort, and the others will be assumed to be forenames, for example the British explorer can be sorted under T as

  author = {Ranulph {Twisleton Wykeham Fiennes}},

• Multiple authors MUST go in a single author field, separated by the literal word and (see example below)

• Values which are purely numeric (eg years) may omit the curly braces;

• Months and editions MUST be numbers (and may therefore omit the curly braces); DO NOT include ordinal indicators like th or st;

• Fields MAY occur in any order but the format MUST otherwise be strictly observed;

• Fields which are not used do not have to be included (so if your editor automatically inserts them as blank or prefixed by OPT [optional], you MAY safely delete them as unused lines)

There is a required minimum set of fields for each of a dozen or so types of document: book, article (in a journal), article (in a collection), chapter (in a book), thesis, report, conference paper (in a Proceedings), etc, exactly as with all other reference management systems. These are all (entry types and entry fields) listed in detail in the biblatex documentation (Lehman, Kime, Boruvka & Wright, 2015, sections 2.1 & 2.2 p.8).

Here’s another example, this time for a book on how to write mathematics — note the multiple authors separated by and. Long entries can spread over several lines: the extra spaces and line-breaks are ignored, so long as the value ends with the matching curly brace (and comma, if needed).

@book{mathwrite, 
  author    = {Donald E Knuth and Tracey
	       Larrabee and Paul M Roberts}, 
  title     = {{Mathematical Writing}}, 
  publisher = {Mathematical Association of America}, 
  address   = {Washington, DC}, 
  series    =  {MAA Notes 14}, 
  isbn      = {0-88385-063-X}, 
  year      = 1989 
}

Every reference in your reference database MUST have a unique key value (label or ID): you can make this up, just like you do with normal cross-references, but some bibliographic software automatically assigns a value, usually based on an abbreviation of the author and year. These keys are for your convenience in referencing: in normal circumstances your readers will not see them. You can see these labels in the right-hand-most column and at the bottom of the screenshot in Figure 5.1 below, and in the examples above. You use these labels in your documents when you cite your references (see § 5.3.2.3 below).

There are many built-in options to the biblatex package for adjusting the citation and reference formats, only a few of which are covered here. Read the package documentation for details: it is possible to construct your own style simply by adjusting the settings, with no programming required (unlike the older BIBTEX styles, which are written in a programming language used nowhere else).

Many users keep their BIBTEX files in the same directory as their document[s], but it is also possible to tell LATEX and BIBTEX that they are in a different directory. This is a directory specified by the $BIBINPUTS shell or environment variable set up at installation time. On Unix & GNU/Linux systems (including Apple Macintosh OS X), and in TEX Live for Windows, this is your TEX installation’s texmf/bibtex/bib directory — the same one that old-style BIBTEX .bst style files are kept in — but to avoid permission conflicts you should use your Personal TEX Directory and create a subdirectory of the same name in there for your own .bib files. MiKTEX also uses the same $BIBINPUTS variable, but it is not set on installation: you need to set it using the Windows Systems Settings (see for example https://www.computerhope.com/issues/ch000549.htm).

5.3.2.3 Citation commands

The basic command is \cite, followed by the label of the entry in curly braces. You can cite several entries in one command: separate the labels with commas.

\cite{fg} 
\cite{bull,davy,heller}

For documents with many citations, use the Cite button or menu item in your bibliographic reference manager, which will insert the relevant command for you (you can see it activated for the TEXStudio editor in Figure 5.1 below).

How the citation appears is governed by two things:

1. the reference format (style) you specify in the options to the biblatex package (see § 5.3.2.4 below)

2. the type of citation command you use: \cite, \textcite, \parencite, \autocite, \footcite, etc, as shown below.

There are four built-in formats in biblatex:

1. authoryear

There are two basic types of author–year citation:

a. author as text, year in parentheses

used in phrases or sentences where the name of the author is part of the sentence, and the year is only there to identify what is being cited; this command is \textcite{fg}

...as has clearly been shown by Fothergill (1929).

This is sometimes called ‘author-as-noun’ citation.

b. whole citation in parentheses

used where the phrase or sentence is already complete, and the citation is being added in support: this command is \parencite{fg}

...as others have already clearly shown (Fothergill, 1929).

The references at the end of the document are sorted into surname order of the first author, and by year after that.

2. numeric

This format is popular in some scientific disciplines where \cite produces just a number in square brackets, eg [42]. The references at the end of the document are usually numbered either in order of citation or in order of first surname;

3. alphabetic

This format is also popular in some scientific disciplines and \cite produces a three- or four-letter abbreviation of the author’s name and two digits of the year, all in square brackets, eg [Fot29]. The references at the end of the document are sorted using abbreviated key value as their label. This format is also called ‘abbreviated’.

4. footnoted

Footnoted citations are common in History and some other Humanities disciplines, to the extent that scholars in these fields actually call their references ‘footnotes’. The command \footcite produces a superscript number like an ordinary footnote, and a short reference at the foot of the page. It is only relevant when using author-year styles (in numeric style it would just produce the reference number at the foot of the page, which would be misleading). The references at the end of the document are given in full, and are usually sorted alphabetically by first surname.

To direct your reader to a specific page or chapter, you can add a prefix and/or a suffix as optional arguments in square brackets before the label.

...as shown by \textcite[p 12]{mathwrite}.

A prefix gets printed at the start of the citation and the suffix gets printed at the end, but all still within the parentheses, if any. As they are both optional arguments, and as suffixes are far more common than prefixes, when only one optional argument is given, it is assumed to be the suffix. The example above therefore produces:

...as shown by Knuth, Larrabee & Roberts (1989, p 12).

There are many variant forms of the citation commands, either for specific styles like Chicago, Vancouver, Harvard, IEEE, APA, MLA, etc; or for grammatical modifications like capitalising name prefixes, omitting the comma between name and year, or adding multiple notes; or for extracting specific fields from an entry (eg \titlecite). If you have requirements not met by the formats described here, you can find them in the documentation for the biblatex package.

Modern Language Association (MLA) citation is a special case, as it omits the year and instead REQUIRES the location of the citation within the document (eg the chapter, section, page, or line). It may include the title, if there would otherwise be ambiguity. The biblatex format for MLA citation handles the context-dependent formatting with the command \autocite.

Figure 5.1: JabRef displaying a file of references, ready to insert a citation of Fothergill’s book into a LATEX document being edited with TEXStudio

Your reference management software will have a display something like Figure 5.1 above (details vary between systems, but they all do roughly the same job in roughly the same way), showing all your references with the data in the usual fields (title, author, date, etc).

Your database, which contains all your bibliographic data, MUST be saved or exported as a BIBTEX format (.bib) file from your reference management software (JabRef uses this format automatically), It looks like the examples in § 5.3.2.2 above. Your .bib file works with both biblatex and BIBTEX, but biblatex provides more field types and document types so that your references can be formatted more accurately.

If your bibliographic management software doesn’t save BIBTEX format direct, save your data in RIS format, then import the .ris file into JabRef and save it as a .bib file from there.

Cheatsheet

Clea F Rees has written an excellent cheatsheet with virtually everything on it that you need for quick reference to using biblatex. This is downloadable as the package biblatex-cheatsheet from CTAN.

Exercise 5.1 — Using biblatex

5.3.2.4 Setting up biblatex with biber

For more complex citation requirements, you may need to set up your document with the following packages:

1. the babel or polyglossia package with appropriate languages, even if you are only using one language. The default language is American English, so there are commands to map this to other language variants (the example below shows this for British English)

2. the csquotes package, which automates the use of quotation marks around titles or not, depending on the type of reference;

3. the biblatex package itself, specifying the biber program and the style of references you want, either numeric, alphabetic, or authoryear; or a publisher’s style; and any options for handling links like DOIs, URIs, and ISBNs;

4. the language mapping command, if needed (see the documentation for the style you have chosen to find out if you need this)

5. finally, the name of your BIBTEX file[s] (see the sidebar ‘Bibliographic reference databases’ above) with one or more \addbibresource commands.

\usepackage[frenchb,german,british]{babel}
\usepackage{csquotes}
\usepackage[backend=biber,doi=true,isbn=true,
            url=true,style=apa]{biblatex}
\DeclareLanguageMapping{british}{british-apa}
\addbibresource{myrefs.bib}

At the end of your document you can then add the command \printbibliography (or elsewhere that you want the full list of references you have cited to be output). See § 5.3.2.5 below for details of how LATEX produces the references.

Versions of biber and biblatex

One critically important point to note is that biblatex and biber are step-versioned; that is, each version of the biblatex package only works with a specific version of the biber program. There is a table of these dependencies in the biblatex documentation PDF. If you manually update biblatex for some reason (perhaps to make use of a new feature), you MUST also update your copy of biber to the correct version, and vice versa, otherwise you will not be able to produce a bibliography.

5.3.2.5 Producing the references

Because of the record→extract→format process (the same as used for cross-references), you will get a warning message about ‘unresolved references’ the first time you process your document after adding a new citation for a previously uncited work. LATEX inserts the label of the reference in bold as a marker or placeholder until you run biber and re-typeset the document. This is why most editors have a Build function to do the job for you.

This function should therefore handle the business of running biber and re-running LuaLATEXfor you. If not, here’s how to do it manually in a Command window: you run LuaLATEXthen run biber to extract and sort the details from the BIBTEX file, and then run LuaLATEXagain:

lualatex myreport 
biber myreport 
lualatex myreport

In practice, authors tend to retypeset their documents from time to time during writing anyway, so they can keep an eye on the typographic progress of the document. So long as you remember to click the Build or equivalent button after adding a new \cite command, all subsequent runs ofLuaLATEXwill incrementally incorporate all references without you having to worry about it.

If you work from the command line, the latexmk script automates this, running bibtex or biber and re-running LATEX again when needed.