%% 
%%  The LaTeX Graphics Companion, 2ed (first printing May 2007)
%% 
%%  Example 6-3-22 on page 376.
%% 
%%  Copyright (C) 2007 Michel Goossens, Frank Mittelbach, Denis Roegel, Sebastian Rahtz, Herbert Vo\ss 
%% 
%%  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.
%% 

\documentclass{ttctexa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{183.83385pt}
\StartShownPreambleCommands
\usepackage{pstricks,pst-tree}
\renewcommand\psedge[2]{%
  \nccurve[angleA=0,angleB=180]{->}{#1}{#2}}
\newcommand\psedgeDash[2]{%
   \nccurve[angleA=0,angleB=180,%
       linestyle=dashed]{->}{#1}{#2}}

\StopShownPreambleCommands
\begin{document}
\pstree[treemode=R,levelsep=3cm]{\Tcircle{0}}{%
  \Tcircle{1}  \Tcircle{2}
  \Tcircle[edge=\psedgeDash]{3}
  \Tcircle[edge=\psedgeDash]{4}}%
\end{document}