%% 
%%  The LaTeX Graphics Companion, 2ed (first printing May 2007)
%% 
%%  Example 7-4-31 on page 500.
%% 
%%  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,arc,dvips]{xy}
\StopShownPreambleCommands
\begin{document}
\[\begin{xy} /r12mm/:
   (0,0)*@{*}="c",*++++!R{c}
  ,(1.2,.8)*+[][F]@{+}="p"
  ,*++!LD{p},"p";"c"**@{--}
  ,{\ellipse<>{}}
  ,{\ellipse(0.8){}}
  ,0;(-1,1)::
  ,{\ar@{.>} 0;(1,0)}
  ,{\ar@{.>} 0;(0,1)}
  ,"p";"c",{\ellipse(.8){--}}
  ,{\ellipse<3mm>{=}}
\end{xy}\]
\end{document}