[texhax] citation in theorem

[Jay H Beder]

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.

Thanks,
Jay


-- 
Jay H. Beder, Professor                        EMS E485
Department of Mathematical Sciences            414-229-5280
University of Wisconsin-Milwaukee              beder at uwm.edu
P. O. Box 413                                  https://pantherfile.uwm.edu/beder/www/
Milwaukee, WI  53201-0413