The WeekBr Med J (Clin Res Ed) 1982; 284 doi: https://doi.org/10.1136/bmj.284.6328.1570 (Published 22 May 1982) Cite this as: Br Med J (Clin Res Ed) 1982;284:1570
Log in using your username and password
Log in through your institution
Register for a free trial to thebmj.com to receive unlimited access to all content on thebmj.com for 14 days.
Sign up for a free trial