% Fichier exo4.16.tex - Ch. Rolland/O Reilly France
\documentclass{article}
\usepackage[latin1]{inputenc}
\begin{document}
$$
\sum_{{\scriptstyle 1\le i\le p
       \atop \scriptstyle 1<j<q}
       \atop \scriptstyle 1\le k< r}
      a_{ij}b_{jk}c_{ki}
$$
\end{document}
