%% 
%%  Ein Beispiel der DANTE-Edition
%%  
%%  2. Auflage
%% 
%%  Beispiel 06-03-25 auf Seite 229.
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%%  Copyright (C) 2016 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
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%% 
\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{145.16928pt}
\setlength\parskip{10pt}
\AtBeginDocument{\setbox0\hbox{$ $}}
%StartShownPreambleCommands
\usepackage{blkarray}
%StopShownPreambleCommands
\begin{document}
\begin{blockarray}{cccc}
11 & 21 & 31 & 41\\
\begin{block}{c | cc \} c}
12 & 22 & 32 & 42\\ 13 & 23 & 33  & 43\\
\end{block}
14 & 24 & 34 & 44
\end{blockarray}
\end{document}