Interactive SETL by Gary Levin CLutx.CLarkson.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)