Aiming to be useful for identifying gaps in core reference collections, for filling out a particular subject area, for determining what to weed out and what to keep, and for checking for new editions and related materials, this bibliography should be a handy reference for all information professionals seeking to build up a quality reference collection. Approximately 1,000 entries have been culled from the more than 8,500 entries appearing in ARBA 1987-1991, covering reference titles with imprints of 1986-1990. Titles have been chosen on the basis of their usefulness to practising librarians. The lengthy reviews have been updated and in some instances, completely rewritten to reflect new editions, with expanded coverage, additional citations to published reviews, and price changes.