<html><head><meta name="color-scheme" content="light dark"></head><body><pre style="word-wrap: break-word; white-space: pre-wrap;">\documentclass{ppex}
\nonstopmode
\usepackage [all,poly,knot,dvips]{xy}
\pagestyle{empty}
\setlength\textwidth{183.0pt}
\begin{document}
\ResetPreambleCommands
\ReadyForTheFray
\usepackage [all,poly,knot,dvips]{xy}
\[\UseTips
\renewcommand{\objectstyle}{\scriptstyle}
\renewcommand{\labelstyle}{\scriptstyle}
\begin{xy} /r9mm/:
  \vover\vcross\vcross\vover-
\end{xy}
\hspace{1cm}
\begin{xy} /r9mm/:
  \vunder&lt;&gt;&lt;{x_i}|&gt;|{y_i}&gt;&gt;&gt;{z_i}%
  \vtwist|&gt;&lt;&lt;\vtwist
  \vunder-&lt;&gt;&lt;{x_o}|&gt;|{y_o}&gt;&gt;&gt;{z_o}%
\end{xy}\]
\end{document}
</pre></body></html>