%% 
%%  Ein Beispiel der DANTE-Edition
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%%  2. Auflage
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%%  Beispiel 09-07-48 auf Seite 438.
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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.
%% 
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% Show page(s) 1
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\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{169.16928pt}
\AtBeginDocument{\setlength\parindent{0pt}}
\setcounter{equation}{66}
\renewcommand\theequation{9.\arabic{equation}}
%StartShownPreambleCommands
\usepackage{amsmath}
%StopShownPreambleCommands
\begin{document}
\begin{align}
\sum_{\substack{1\le i\le p\\
    1\le j\le q\\ 1\le k\le r}%
  }a_{ij}b_{jk}c_{ki}
\end{align}
\end{document}