\documentclass[12pt,reqno]{article}

\def\amod#1 #2{#1\ ({\rm mod}\ #2)}

\begin{document}

\begin{abstract}
Given a pair $(U_t)$ and $(V_t)$ of Lucas sequences, Kimball and Webb
showed that $\sum_{0<t<\rho_U}\frac{V_t}{U_t} \equiv \amod{0} {p^2}$, if
$p$ is a prime $\ge5$ whose rank $\rho_U$ is maximal, that is to say,
$\rho_U$ is $p$ or $p\pm1$. We extend their result replacing $p$ by a
composite integer $m$ of maximal rank, thereby providing a
generalization of a classical congruence of Leudesdorf.
\end{abstract}


\end{document}
