This collection of three supplements was based on DC's own series and which covered only the first 13 volumes out of 18 in all. This, on the DC series, from Wikipedia:
In 1990, DC started over with a new Who's Who series titled Who's Who in the DC Universe (16 loose-leaf issues with binders sold separately, cover dated August, 1990 to February, 1992). [...] This series was followed up by Who's Who in the DC Universe Update 1993 (2 loose-leaf issues, cover dated December, 1992 and January, 1993).
for additional information see Wikipedia