%% 
%%  Example 04-01-2 
%%  Copyright (C) 2016 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{328.62788pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{amsmath,amscd}
%StopShownPreambleCommands
\begin{document}
\[
\begin{CD}
  R\times S\times T @>\text{restriction}>> S\times T \\
        @VprojVV                            @VVprojV \\
  R\times S         @<<\text{inclusion}<        S
\end{CD}
\]
\end{document}
