# cross-referencing in the appendix, imsart package

I have a problem running the following code, which uses imsart package and aop option:

\documentclass[aop]{imsart}
\newtheorem{theorem}{Theorem}[section]
\begin{document}
\begin{theorem}\label{thm}
This is a Theorem.
\end{theorem}
\begin{appendix}
\section{Proof to Theorem \ref{thm}}
Proof of Theorem \ref{thm}
\end{appendix}
\end{document}


The outcome is this:

it fails to add the hyperlink to the theorem in the title of the appendix. Any solution?

After \appendix, \section is redefined to apply \MakeUppercase to each title, which has the unfortunate consequence of uppercasing also thm.

Indeed, you get

LaTeX Warning: Reference THM' on page 1 undefined on input line 11.


You can work around the issue by loading textcase with the overload option, that will avoid \MakeUppercase touching the argument to \ref.

\documentclass[aop]{imsart}

\newtheorem{theorem}{Theorem}[section]

\begin{document}
\begin{theorem}\label{thm}
This is a Theorem.
\end{theorem}

\appendix
\section{Proof to Theorem \ref{thm}}
Proof of Theorem \ref{thm}

\end{document}


By the way, there is no appendix environment defined. Just the \appendix` declaration.

• The perfect answer, thank you!
– mmg
Mar 11, 2020 at 14:58