The author would like to express his appreciation to Bonnie Dorr for the support and insight that led to this work, to Wade Shen for his assistance with term alignment, to David Hull of Rank Xerox Research Centre for his assistance with preprocessing the document collections, and to the Logos corporation for machine translation support. This work has been supported in part by DOD contract MDA9043C7217, ARPA and ONR contract N00014-92-J-1929, ARPA contract DACA76-92-C009 and NSF award IRI-9357731.