%% 
%%  An UIT Edition example
%% 
%%  Example 09-03-2 on page 169.
%% 
%%  Copyright (C) 2010 Herbert Voss
%% 
%%  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.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{375.57637pt}
\AtBeginDocument{\setlength\parindent{0pt}}
\setcounter{equation}{1}
\renewcommand\theequation{9.\arabic{equation}}
\StartShownPreambleCommands
\usepackage{amsmath,amscd}
\newcommand\cov{\operatorname{cov}}\newcommand\non{\operatorname{non}}
\newcommand\cf{\operatorname{cf}}  \newcommand\add{\operatorname{add}}
\StopShownPreambleCommands
\begin{document}
\begin{equation}
\begin{CD}
  \cov(\mathcal{L}) @>>> \non(\mathcal{K}) @>>> \cf(\mathcal{K}) @>>>
  \cf(\mathcal{L})\\
  @VVV @AAA @AAA @VVV\\
  \add(\mathcal{L}) @>>> \add(\mathcal{K}) @>>> \cov(\mathcal{K}) @>>>
  \non(\mathcal{L})
\end{CD}
\end{equation}
\end{document}