1. Electronic bibliographic databases searched.

Sources searched

1. AMED 2. Best Evidence 3. Biological Abstracts 4. CCTR (Cochrane Controlled Trials Register) ( last searched Issue 3, 2001) 5. CDSR (Cochrane Database of Systematic Reviews) 6. EMBASE 7. HMIC (Health Information Management Consortium ‐ comprising DH‐Data, the King's Fund Database, and Helmis) 8. Medline 9. NHS DARE (Database of Assessments of Reviews of Effectiveness) 10. NHS EED (Economic Evaluations Database) 11. NHS HTA (Health Technology Assessment) 12. PubMed (last 180 days) 13. Science Citation Index