%% The LaTeX Graphics Companion, 2ed (first printing May 2007)

%%
%% The LaTeX Graphics Companion, 2ed (first printing May 2007)
%%
%% Example 7-4-34 on page 502.
%%
%% 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{207.83385pt}
\StartShownPreambleCommands
\usepackage[all,web]{xy}
\StopShownPreambleCommands
\begin{document}
\[\renewcommand{\latticebody}{\drop@{o}}
\begin{xy}
*\xybox{0;<5mm,2mm>:<2mm,5mm>::
,0,{\xylattice{-3}{3}{-3}{3}}}="S"
,{"S"+L \ar "S"+R*+!L{z_1}}
,{"S"+D \ar "S"+U*+!D{z_2}}
\end{xy}\]

\end{document}