%% 
%%  Ein Beispiel der DANTE-Edition
%% 
%% 
%%  Copyright (C) 2010 Herbert Voss
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{166.324pt}
\setlength\parindent{0pt}
\StartShownPreambleCommands
\usepackage{pst-node}
\StopShownPreambleCommands
\begin{document}
$\psmatrix[mnode=dia,colsep=1cm]
     & [mnode=circle] X \\
   Y & Z
 \endpsmatrix \psset{nodesep=3pt,arrows=->}
 \ncline{1,2}{2,1}  \ncline{1,2}{2,2}
 \ncline[linestyle=dotted]{2,1}{2,2}$
\end{document}