I have used \newtheorem to define a class. I want to modify a previous instance of the class to present a slight variation. (A similar, but different, example is using a previous equation to number the current one.) Here is an example of the output I would like:
Assumption 1. An assumption.
Assumption 1'. A similar assumption.
I have tried using \tag with no success. Here is an example of my failed attempts:
\documentclass[11pt]{article}
\usepackage{amsmath}
\newtheorem{assumption}{Assumption}
\begin{document}
\begin{assumption}
\label{a1}
An assumption.
\end{assumption}
\begin{assumption}
\label{a1'}
A similar assumption.
\tag{\ref{a1}'}
\end{assumption}
\end{document}
My main interest is not in getting \tag to work, but in finding some (preferably simple) way to get numbering like this. Any help would be appreciated.
