\documentclass{ppex}
\nonstopmode
\usepackage [curve,knot,arrow,dvips]{xy}
\pagestyle{empty}
\setlength\textwidth{183.0pt}
\begin{document}
\ResetPreambleCommands
\ReadyForTheFray
\usepackage [curve,knot,arrow,dvips]{xy}
\[\renewcommand{\labelstyle}{\scriptstyle}
\begin{xy} 0;/r8mm/:
 ,{\xcapv-|{a}}
 , +(0,1) ,{\xcaph|{b}\xunderh|{c}%
         \xcaph|{d}\xcapv|{e}}
 ,-(3,0),{\xoverh|{f}}
 ,+(1,0),{\xoverh|{g}}
 ,-(3,1),{\xcapv-|{h}\xcaph-|{i}}
 ,+(0,1),{\xunderh-|{j}}
 ,+(0,-1),{\xcaph-|{k}}
 ,+(0,1),{\xcapv|{l}}
\end{xy}\]
\end{document}
