%% 
%%  The LaTeX Graphics Companion, 2ed (first printing May 2007)
%% 
%%  Example 7-4-15 on page 488.
%% 
%%  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[graph,frame]{xy}
\StopShownPreambleCommands
\begin{document}
\[\xygraph{
[] *+[o]+[F]{1}
  (-[dl] *+=[o]+[F]{11}
  ,-[d]  *+=[o]+[F]{12}
    (-[dl] *+=[o]+[F]{121}
    ,-[d]  *+=[o]+[F]{122}
    ,-[dr] *+=[o]+[F]{123}
    )
  ,-[dr] *+=[o]+[F]{13}
  )
}\]
\end{document}
