I use biblatex with biber backend to cite BibTeX entries exported from Mendeley Desktop. Every time I try to render a citation with \cite or \printbibliography or anything else, I get warnings like

LaTeX Warning: Citation 'VanDijk2018' on page 3 undefined on input line 10.
LaTeX Warning: There were undefined references.

I'm using Overleaf. It detects all entries correctly as it suggests me autocompletion for the \cite command. So the file structure seems ok.

I can't figure why it doesn't work then. Thank you for your help.


1 Answer 1


The Overleaf's support helped me. The problem was due to special hidden caracters in the 'annote' and 'abstract' fields, which probably came from copy-pastes of PDF files. These caracters caused biber to fail.

The problem is solved by removing the two fields from all my BibTeX entries. They are useless for a citation file.

Due to the high number of entries, I have written a Python 3 script that cleans the files automatically. The script also changes the format of the 'month' fields with numbers instead of strings (jan, Feb. and so on). Feel free to use and modify. https://gist.github.com/alexandrehuat/6d3263f73ccae87d0107977978316c02

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