%% 
%%  Example 04-01-1 
%%  Copyright (C) 2016 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{158.31393pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{amsmath,accents}
%StopShownPreambleCommands
\begin{document}
\underline{$M$}\quad\underbar{$M$}
\quad$\underaccent{\bar}{M}$
\end{document}
