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Thanks a lot. That does the trick. Well, should have thought about it myself. Again, that was very helpful.

Hello,
I have the following code:

\begin{theorem}[Schmith theorem, see \cite[Theorem 3.1]{book}]
...
\end{theorem}

This results in the following error:

>ERROR: Argument of \@citex has an extra }.
>
>--- TeX said ---
><inserted text>
> \par
>l.2641 ...[Schmith theorem, see \cite[Theorem 3.1 ...