BibTeX FAQ

How do I cite a website?

Classic BibTeX has no dedicated type for web pages, so use @misc and put the URL in howpublished, adding the access date as a note:

@misc{ctan-bibtex,
  author       = {{CTAN}},
  title        = {The {BibTeX} package},
  howpublished = {\url{https://ctan.org/pkg/bibtex}},
  note         = {Accessed: 2026-09-29},
  year         = {2026}
}

Load the url or hyperref package for \url. Styles like plainnat also print a url field directly. With biblatex, use @online with the url and urldate fields instead.

Why are the capital letters in my titles lost?

Many styles convert titles to sentence case. Protect proper nouns and acronyms with braces: title = {A History of {NASA} and the {Apollo} Program}. See protecting capital letters.

How do I list several authors, or write “et al.”?

Separate every name with and, never with commas: author = {Knuth, Donald and Lamport, Leslie}. To shorten a long list in the .bib file itself, end it with and others, which styles print as et al. Most styles also abbreviate long author lists in citations on their own.

How do I enter an organization as author?

Wrap the name in a second pair of braces so BibTeX doesn’t split it into first and last names: author = {{European Space Agency}}.

Why do I get “Citation undefined” or an empty bibliography?

Usually because BibTeX didn’t run, or LaTeX didn’t run again afterwards. Compile LaTeX, BibTeX, LaTeX, LaTeX as described in Using BibTeX. If that doesn’t help, check:

• \bibliography{references} names your file without the .bib extension, and the file can be found.
• There is exactly one \bibliographystyle command.
• The citation key is spelled exactly as in the .bib file (keys are case-sensitive in some tools).
• The .blg log file doesn’t report errors.

Why is an entry missing from my bibliography?

BibTeX only includes entries you cite. Use \nocite{key} for single entries or \nocite{*} for everything in the file. If the entry has a syntax error, BibTeX may skip it, so check the .blg file.

What does “I was expecting a ,' or a }’” mean?

BibTeX found something unexpected inside an entry, most often a missing comma between two fields, an unbalanced brace, or a " inside a quoted value. The message includes the line number in your .bib file. Look at the line before the one reported too.

What’s the difference between BibTeX, biblatex and biber?

BibTeX is both the file format and the original program (1985) that turns .bib files into bibliographies using .bst styles. biblatex is a LaTeX package that does the formatting in LaTeX instead. biber is the program biblatex uses to read and sort .bib files, with full Unicode support. All three use the same file format. See BibTeX or biblatex?

How do I get BibTeX entries for papers?

Paste the DOI or arXiv ID into the DOI → BibTeX lookup. Google Scholar, publisher pages and arXiv also offer a “Cite” or “Export BibTeX” link. Whatever the source, check the result: capitalization and special characters often need fixing.

What citation key should I use?

Anything unique works, but a consistent scheme helps you remember keys. Two popular schemes are author+year+first title word, as in knuth1984texbook (Google Scholar’s style), and Knuth1984. Avoid spaces, commas and non-ASCII characters in keys.

How do I order references by appearance instead of alphabetically?

Use a style that doesn’t sort: unsrt, ieeetr, or unsrtnat with natbib. With biblatex, pass sorting=none.

Can I use BibTeX with Word?

Not directly, but reference managers bridge the gap. Import your .bib file into Zotero or JabRef and use their Word or LibreOffice plugin to insert citations and bibliographies. See tools.