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
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16