%% 
%%  A DANTE-Edition example
%% 
%%  Example 16-08-3 on page 260.
%% 
%%  Copyright (C) 2011 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[]{article}
\pagestyle{empty}
\setlength\textwidth{177.70511pt}
\setlength\parindent{0pt}

\usepackage{pstricks,pst-node}

\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}
