no \bibdata command, no \bibstyle command



Hi!
This is the last part of my main file in latex:

\include{copy1}
\cleardoublepage
\include{copy2}
\cleardoublepage
\bibliographystyle{author3}
\bibliography{correlati04}

\end{document}

When I run bibtex the following error appears:
no \bibdata command
no \bibstyle command

This is BibTeX, Version 0.99cThe top-level auxiliary file: atti.aux
A level-1 auxiliary file: copy1.aux
A level-1 auxiliary file: copy2.aux
I found no \bibdata command---while reading file atti.aux
I found no \bibstyle command---while reading file atti.aux
(There were 2 error messages)

I tried to use the plain style but the result is the same.
Please help me!
Thanks
Silvia

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