Okapi at TREC-2. - Stephen E. Robertson; Steve Walker; Susan Jones; Micheline Hancock-Beaulieu; Mike Gatford (TREC, 1993)

Okapi at TREC-3. - Stephen E. Robertson; Steve Walker; Susan Jones; Micheline Hancock-Beaulieu; Mike Gatford (TREC, 1994)

Okapi at TREC-4. - Stephen E. Robertson; Steve Walker; Micheline Hancock-Beaulieu; Mike Gatford; A. Payne (TREC, 1995)

Interactive Thesaurus Navigation: Intelligence Rules OK? - Susan Jones; Mike Gatford; Stephen E. Robertson; Micheline Hancock-Beaulieu; Judith Secker; Steve Walker (J. Am. Soc. Inf. Sci., 1995)

Okapi at TREC-5. - Micheline Hancock-Beaulieu; Mike Gatford; Xiangji Huang 001; Stephen E. Robertson; Steve Walker; P. W. Williams (TREC, 1996)

Interactive Okapi at TREC-6. - Micheline Hancock-Beaulieu; Mike Gatford (TREC, 1997)

Transaction logging. - Susan Jones; Mike Gatford; Thien Do; Steve Walker (J. Documentation, 1997)

Peeling the onion: Okapi system architecture and software design issues. - Susan Jones; Steve Walker; Mike Gatford; Thien Do (J. Documentation, 1997)