%% 
%%  Ein Beispiel der DANTE-Edition
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%%  1. Auflage
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%%  Beispiel 15-04-22 auf Seite 802.
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%%  Copyright (C) 2011 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{118.324pt}
\usepackage[T1]{fontenc}
\StartShownPreambleCommands
\usepackage{tikz}
\StopShownPreambleCommands
\begin{document}
\begin{tikzpicture}[Kreis/.style={circle,draw=blue!50,fill=blue!20,thick},
   Rechteck/.style={rectangle,draw=black!50,fill=black!20,thick},bend angle=45,
   pre/.style={<-,shorten <=1pt,semithick}, post/.style={->,shorten >=1pt,semithick}]
\node[Kreis] (K1) {};               \node[Kreis]     (K2) [below of=K1] {};
\node[Kreis] (K3) [below of=K2] {}; \node[Rechteck] (R_1) [right of=K2] {}
 edge [pre] node[auto] {1} (K2) edge [post,bend  right] node[auto,swap] {2}(K1)
 edge [pre, bend left] node[auto] {3} (K3);
\node[Rechteck] (R_2) [left of=K2] {} edge [post] node[auto] {A} (K2)
 edge [pre, bend left] node[auto] {B} (K1) edge [post,bend right] node[auto,swap] {C}(K3);
\end{tikzpicture}
\end{document}