Cross-referencing, Citations, and BibTeX

Overview

Teaching: 0 min
Exercises: 0 min

Questions

• How do I cite my sources in LaTeX?

Objectives

• Create a Table of Contents

• Create a List of Figures

• Create a List of Tables

• Create an Appendix

• Cross-reference within your text

• Explain BibTeX

• Import a BibTeX file into a document

• Create a bibliography

• Cite an article in-line

• Cite as a footnote

• Change the way citations are represented in the bibliography and in the text

When constructing a large document such as a book or a thesis, we must often reference the contents, tables, and figures we are using elsewhere in the document. LaTeX allows us easily perform both indexing and cross-referencing.

Indexing

The indexing covered here will include the simple methods by which lists of content can be added to a document. While it is possible to create detailed indexes, such as one would find in the back of a textbook, that will not be covered here.

Table of Contents, List of Figures, List of Tables

All section, subsection, and similar hierarchal headings are numbered automatically by LaTeX. A list of these contents can be generated using a table of contents by issuing the tableofcontents command. The table will generate with the name of each section heading and a corresponding page number.

Similarly, a list of the figures and tables used in the document can be generated using listoffigures and listoftables, respectively. Each add a reference to the automatically generated figure or table number, and include a page number for reference.

It is worth nothing that any section*, figure*, table*, or other environment starred (*) to prevent increasing the counter will not appear on these indexes, nor will the numbering of items in the index increase, showing a gap where a starred item is.

It is possible to change the numbering of index items manually. This is useful in cases such as telling LaTeX to interpret a “preface” type section as the 0th section or jumping values to work on a certain “chapter”. These can be modified using the setcounter command. The setcounter command takes two arguments in separate curly braces. The first argument is the type of object you want to change the number of (e.g. subsection, figure, or table), and the second argument is the value you want to set it at. For example, if you issue \setcounter{table}{3}, the next table will be Table 4.

It is possible to ignore certain sub- levels in an index with setcounter. By issuing the first argument as tocdepth and the second argument 5, the table of content will show sub-sub-sub-sub-section level content with page numbers (this type of section is called paragraph when issuing sectioning commands).

Appendices

It is possible to create sections with a unique numbering scheme. There are some advanced uses of this we will not cover here, but there is a notable common use. When an appendix command is issued once, LaTeX will treat every section added below that line as an Appendix. Depending on the documentclass you are using, appendices may be ignored altogether or be numbered in a unique way such as “A1, A2, etc.

Abstracts

Research documents and many other academic publications will require the use of an abstract. The abstract environment will alter the formatting of the content contained within it to match the style of the documentclass, but it will not be added to any indexes. Often, there are unique requirements for issuing the abstract command in a documentclass supplied by an academic publisher. Remember to read all of the documentation so that your paper meets the content guidelines.

Cross Referenes

Cross-referencing within the text of a document is used to tell the audience which table, figure, or section you are referencing. Since LaTeX issues the numbers of these environments dynamically, we need to label them in a meaningful way. Inside each environment you may reference, usually on the first line of that environment, a label command can be issued with some unique identifier within the curly braces. While the unique identifier can be anything you choose, there is a standard convention to include a type before the identifier, making a label for some arbitrary figure read: \label{fig:arbitrary}. A list of the standardized label types are:

These standards are useful for reading the LaTeX code when you have forgotten the exact meaning, and for keeping anyone reviewing your work informed. We all know how important it is to keep reviewers happy!

To reference something you have labeled in the text, simply use the ref command with your identifier. This will place a reference exactly where you tell it in the body of the text to whatever dynamically numbered thing you are referencing.

There are techniques to label and reference portions of your document in more advanced ways, such as labeling of individual steps in a multiline equation, but that is considered an advanced topic.

Citations and Bibliographies

BibTeX Files

Information for LaTeX works cited in the paper is stored in a special file (.bib filetype) in the BibTeX format. The format stores information about the title, author, year, url, and other relevant information for publications you intend to cite. Each BibTeX entry is given a type, such as journal article, web-page, report, etc., and a unique identifier. When information is cited in the LaTeX document by referencing the identifier, LaTeX and BibTeX parse the file for the type of each entry. Then, based on the settings in the LaTeX document, BibTeX prints the relevant information. This means that BibTeX entries can store information that may not be used within the document.

The BibTeX format is very common in academic circles. When an academic paper is accessed from a database online, there is often an option to “export” the citation. If you are using a citation manager (which is highly recommended), you might already be familar with exporting meta files.

Citation managers including Zotero, Mendeley, and EndNote, support exporting libraries as BibTeX files. This makes it particularly easy to collect references you intend to use in a file, and have it ready to go when preparing a document.

Inline Citation

To cite works within the text of your document, use the cite command with the unique identifier of the BibTeX entry you want. This operates similarly to the ref command by putting the inline citation exactly where you declare it. The proper way to format this in your text such that the page rendering does not automatically wrap the citation around to a new line is to use a non-breaking space (~) before each citation command.

This is some text blah blah.~\cite{2008Einstein}

Multiple citations can be placed in a single cite command. Each identifier you want to cite should be separated by a comma (,).

This is some text blah blah.~\cite{2008Einstein, 2009Lamport, 2001Gonzales}

Adding an options to the cite command enclosed in square braces will add text to the inline citation. This is useful for including page or chapter information. Simply place the page number or range of numbers in the brackets to automatically produce the necessary modification.

This is some text blah blah.~\cite[84]{2008Einstein}

Footnote Citation

Certain publication formats will require citations to be placed in the footnotes of the page the inline citation occurs on. LaTeX does not support this natively, so we need to pull in a package which can handle it called footbib. The cite command is replaced by footcite, and has many of the same rules as cite.

This is some text blah blah.~\footcite{2008Einstein}

Creating a Bibliography

Of course, if inline citations are used, there must be a bibliography or works cited section to contain the references. We first declare how the bibliography should look using bibliographystyle. There are several default options available:

On the next line, the command bibliography is issued with curly braces holding the filenames of your BibTeX file. The filetype (.bib) is NOT added. If the BibTeX file is not in same the root directory as your LaTeX file, then you must declare the full path. However, it is recommended to include a unique BibTeX file in the root project directory for each document you create to aid portability.

\bibliographystyle{plain}
\bibliography{bibfile}

There are many more styles of inline and reference citations available outside of the default LaTeX configuration. Some document classes provided by publishers will require certain custom bibliography styles to be used. For these, it is important to read the documentation for to match the requirements of the class. The natbib package is commonly used to provide more options for formatting citations. It operates very similarly to the default BibTeX use we have learned here. Consult the documentation for more information.

Key Points

• Create a Table of Contents with tableofcontents

• Create a List of Figures with lisfoffigures

• Create a List of Tables with listoftables

• Prevent a section from being counted using *

• Change how deep sections are counted using setcounter{tocdepth}

• Declare a region of sections to be numbered as Appendices with appendix

• Reference a figure number in text by labeling it with label and calling it with ref

• Create a BibTeX entry manually with bibitem within thebibliography environment

• Create a bibliography in the text with bibliography and bibliographystyle

• Import a premade .bib file with bibliography

• Create an inline citation number with cite

• Place a citation in a footnote using footnote{cite{}}

• Change they way the citation appears with natbib