%% 
%%  Example 01-06-2 
%%  Copyright (C) 2017 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{158.31393pt}

%StartShownPreambleCommands

%StopShownPreambleCommands
\begin{document}
\begin{equation}
\sum_{{1\le j\le p\atop {%
  {1\le j\le q\atop 1\le k\le r}}}%
}a_{ij}b_{jk}c_{ki}
\end{equation}
\end{document}
