\documentclass{rtaloop}
\rtalabel{cycle-unification}

\begin{document}
\begin{solvedproblem}{Jean-Pierre Jouannaud}{}{June 1993}

\begin{abstract}
Is \emph{cycle unification} decidable?
\end{abstract}
\emph{Cycle unification} has been defined in \cite{BHW92}. Is cycle
unification decidable?
\begin{remark}
  Cycle unification \cite{BHW92} is undecidable
  \cite{Devienne}\cite{HW:ipl}.  This was a long standing open
  problem, related to the non-termination of simple logic programs.
\end{remark}

\end{solvedproblem}
\end{document}