%% 
%%  The LaTeX Graphics Companion, 2ed (first printing May 2007)
%% 
%%  Example 6-2-62 on page 360.
%% 
%%  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{159.83385pt}
\setlength\parindent{0pt}
\StartShownPreambleCommands
\usepackage{pstricks,pst-node}
\StopShownPreambleCommands
\begin{document}
\begin{pspicture}(-0.5,0)(3,3)  \Huge
  \cnode(1,3){4pt}{A}
  \rput[B](0,0){\Rnode{B}{A}}
  \rput[B](2,0){\Rnode{C}{a}}
  \psset{angleA=90,armA=1,nodesepA=3pt}
  \nccurve[angleB=-135]{<-}{B}{A}
  \nccurve[angleB=-45]{<-}{C}{A}
\end{pspicture}
\end{document}