# Author-date referencing overridden [closed]

I'm using the `natbib` package and would like author-date referencing format. I have the following setup in the preamble:

``````\usepackage[authoryear]{natbib}
\bibliographystyle{harvard} %(also tried apalike)
\bibliography{mylibrary}
``````

Compiling leads to number format in the pdf with an error 'Bibliography not compatible with author year citations' and the commands:

``````\providecommand\NAT@force@numbers{}\NAT@force@numbers
``````

in the `.aux` file. I had previously used the author-date format with no trouble so I'm not sure why this error has suddenly occurred. I'm using TeXnicCenter with MiKTeX on Windows 7.

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## closed as too localized by Guido, barbara beeton, egreg, Werner, Torbjørn T.Apr 23 '13 at 5:13

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Have you checked the formatting of the bibliography items. If there is a mistake there, the bibliography can revert to number format. Common mistakes involve mixing up "[" and "{" –  Peter Jansson Jan 23 '13 at 14:29
Thanks for your reply. Do you mean in the bibtex file itself or within the latex document e.g. the \citep commands? –  218 Jan 23 '13 at 20:07
My comment actually came from using \bibitem[]{} in the document file and I am therefore now uncertain how these errors translate into a bib-file. Would it be possible to post a mnimum working example (MWE) of your document and bib-file that reproduces the error? –  Peter Jansson Jan 23 '13 at 20:15
Thanks for your help. It seems that the issue related to an entry in the .bib file which didn't have a date, hence natbib overrode the author-date format. Fixing the problem required repairing the databse but also deleting the .aux and .bbl files otherwise the error persisted even with a corrected database. –  218 Jan 24 '13 at 17:56