Full text
PDF
. 1951 Dec;6(4):560–571. doi: 10.1111/j.1476-5381.1951.tb00667.x
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.