Some problems arising in the combination of discipline-oriented retrieval systems for the purpose of constructing a specialized retrieval system for a multidisciplinary topic are considered. A compromise solution involving an augmented combined index is suggested. (4 references) (Author/NH)

Causes of Boolean failures to retrieve relevant MEDLARS index references are: search formulator failed to include important terms, indexer failed to include important terms, and misunderstanding of user's needs. On the evidence of this test the Probabilistic search is at least a partial solution to these problems. (8 references) (Author/NH)