No. 69 issued in parts labelled wtih an alphabetic suffix. Vols. issued out of alphabetic sequence, some with the earlier series title, others with the later series title.
Discs for 1991- produced for use only on DOS-based computer systems.
System requirements for DOS: IBM or compatible PC (386 processor); 4MB RAM; MS- or PC-DOS version 5.0 or later; VGA color monitor; CD-ROM drive.
System requirements for Macintosh: Macintosh running System 7 or later; 8MB RAM; 13-inch color monitor; CD-ROM drive.