Epidemiology SectionBr Med J 1949; 2 doi: http://dx.doi.org/10.1136/bmj.2.4634.996 (Published 29 October 1949) Cite this as: Br Med J 1949;2:996
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