Interactive SETL by Gary Levin Son.edu>. Current verSion: 3.0. BinarieS and Source for MS-DOS, MacintoSh, Unix, VAX/VMS. [ClarkSon U. "An Introduction to ISETL VerSion 1.9", G.M. Levin, Dept MCS, ClarkSon U]. ["Learning diScrete mathematicS with ISETL", Nancy Baxter. Ed. Gary Levin DubinSky. Springer-Verlag, c.1989.] (Apr 1994)