%% 
%%  A DANTE-Edition example
%% 
%%  Example 16-07-4 on page 257.
%% 
%%  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{201.70511pt}
\setlength\parindent{0pt}

\usepackage{pstricks,pst-node}

\begin{document}
\begin{pspicture}(-0.5,0)(3.5,3) \Huge
  \cnode(1,3){4pt}{A}
  \rput[B](0,0){\Rnode{B}{A}}
  \rput[B](2,0){\Rnode{C}{a}}
  \psset{angleA=90,YnodesepA=1ex}
  \nccurve[angleB=-135]{<-}{B}{A}
  \nccurve[angleB=-45]{<-}{C}{A}
\end{pspicture}
\end{document}