The LancetVolume 338, Issue 8779, 30 November 1991, Pages 1368-1373INFORMATION FOR CLINICIANS: Use and sources of medical knowledgeAuthor links open overlay panelJ. Wyatt MRCPShow moreShareCitehttps://doi.org/10.1016/0140-6736(91)92245-WGet rights and contentUnder a Creative Commons licenseopen archivePrevious article in issueNext article in issueRecommended articlesCited by (0)Copyright © 1991 Published by Elsevier Ltd.