%% 
%%  Ein Beispiel der DANTE-Edition
%%  
%%  7. Auflage
%% 
%%  Beispiel 15-09-3 auf Seite 289.
%% 
%%  Copyright (C) 2016 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
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%% 
\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{169.16928pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{pst-node}
%StopShownPreambleCommands
\begin{document}
$ \psmatrix[mnode=dia,colsep=1cm]
      & [mnode=circle,name=X] X \\[0pt]
    [name=Y] Y & [name=Z] Z
  \endpsmatrix
  \psset{nodesep=3pt,arrows=->}
  \ncline{X}{Y}  \ncline{X}{Z}
  \ncline[linestyle=dotted]{Y}{Z} $
\end{document}