BibTeX isn't working; my \cite are showing up as question marks (?)

This can happen for a number of reasons:

• Have you used any \cite commands in your document? Only bib entries that have been \cite in the main text will appear in the bibliography list.
• Did you specify the correct .bib file name (without extensions) for \bibliography{...}? It's case sensitive, so watch out for typos.
• Have you specified the bibliography style with a \bibliographystyle{...}? If the style isn't a standard one that comes with TeX Live, you will need to upload the .bst file to your project.
• You may have a syntax error in your .bib file that's preventing bibtex from parsing it correctly. If so, there should be some information about this in the warning messages; fix them accordingly and bibtex should be able to read them again.
• Is your .bib file or main .tex file in a folder that has spaces or unusual characters in its name? The main .tex file should always be at the top level, and files in folders with spaces or unusual characters can sometimes not be found by the compile process.
• If you have done all of the above and the citations still are't working: This may also happen in some edge cases, due to how lines are formatted in the .log file and how the build tool reads the file. Adding \typeout{} just before your \bibliography{...} may help.

For more information about BibTeX, take our free online interactive tutorial, or take a look at this video tutorial and Wikibook articles.