1\begin{thebibliography}{9} 2 3\bibitem{melham} % OK 4T.\ F.\ Melham, 5{\it The HOL sets library}, 6University of Cambridge Computer Laboratory, 7October 1991. 8 9\bibitem{description} % OK 10University of Cambridge Computer Laboratory, 11{\it The HOL System: DESCRIPTION}, revised edition, 1991. 12 13\end{thebibliography} 14 15 16