Full text
PDF
. 1952 Oct;9(4):311–313. doi: 10.1136/oem.9.4.311
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.