# [texhax] citation in theorem

Steve Revilak steve at srevilak.net
Mon Jan 17 19:12:49 CET 2011

>In using the "extra title" option in calling a theorem --
>  \begin{theorem}[extra_title]  ... \end{theorem}
>I would like to add a citation:
>  \begin{theorem}[extra_title \cite{einstein05}]  ... \end{theorem}
>LaTex doesn't like this;  the complaint is
>  Argument of \@citex has an extra }.
>Is there a way to make this work?  To be sure, I can always move the citation out of the "extra title" option:
>  \begin{theorem}[extra_title] \cite{einstein05}  ... \end{theorem}
>but that's not quite what I want, and the result looks funny.

Hello Jay,

Could you provide a small example that exhibits this behavior?  I
tried to reproduce your error with a minimial example (which I've
included below), but I was not successful in doing so.  (i.e., my
minimal example compiles without error).

---------------------------------
\documentclass{article}
\usepackage{ntheorem}

\newtheorem{theorem}{Theorem}
\begin{document}

Here is a theorem.

\begin{theorem}[Gnu Theorem \cite{lamport}]
Gnus are big and gnats are small.
\end{theorem}

\begin{thebibliography}{1}
\bibitem[1]{lamport} Lamport, Leslie.  \LaTeX{}: a Document
Preparation System.
\end{thebibliography}

\end{document}
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