%% 
%%  Ein Beispiel der DANTE-Edition
%%  Mathematiksatz mit LaTeX
%%  3. Auflage
%%  Beispiel 09-04-2 auf Seite 176.
%%  Copyright (C) 2018 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[10pt]{screxa}
\pagestyle{empty}
\setlength\textwidth{352.81416pt}
\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}

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