%%
%% A DANTE-Edition example
%%
%% Example 17-01-20 on page 275.
%%
%% 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{153.70511pt}
\setlength\parindent{0pt}
\usepackage{pst-tree,amsmath}
\begin{document}
\pstree[nodesepB=3pt,arrows=->,levelsep=2cm]{%
\Tdia{$\substack{o|o\\\_}$}}{%
\TR[edge={\ncbar[angle=180,armB=0.3cm]}]{$x$}
\TR{$y$}
\TR[edge={\ncbar[armB=0.3cm]}]{$z$}}
\end{document}
