%% 
%%  Example 01-22-3 
%%  Copyright (C) 2017 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{110.31393pt}

%StartShownPreambleCommands

%StopShownPreambleCommands
\begin{document}
\begin{equation}
\sum_{\makebox[0pt]{$
       \scriptscriptstyle 1\le j\le p\atop {1\le j\le q\atop 1\le k\le r}$}%
     }a_{ij}\mathbf{b_{jk}}c_{ki}
\end{equation}
\end{document}
