Research Article
Critical appraisal of published research: introductory guidelines.
British Medical Journal 1991; 302 doi: https://doi.org/10.1136/bmj.302.6785.1136 (Published 11 May 1991) Cite this as: British Medical Journal 1991;302:1136
This is a PDF-only article. The first page of the PDF of this article appears above.