Interactive SETL by Gary Levin .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)