<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,2cell]{xy}
\pagestyle{empty}
\setlength\textwidth{183.0pt}
\begin{document}
\ResetPreambleCommands
\ReadyForTheFray
\usepackage [all,2cell]{xy}
\UseAllTwocells
\[
\xymatrix @=15mm {
  L_1 \rlowertwocell&lt;-3&gt;_{a_1}{&lt;-1&gt;}
      \rcompositemap&lt;6&gt;_{a_2}^{a_3}{\omit}
&amp; R_1 \dtwocell&lt;0&gt;_{a_4}{"}
\\ L_2 \uuppertwocell_u^d{\omit}
       \rtwocell&lt;2&gt;{'id}
&amp;  R_2
 }\]
\end{document}
</pre></body></html>