ISETL Interactive {SETL} by Gary Levin. Current version: 3.0. {Binaries (ftp://sun.soe.clarkson.edu/)} 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)