Full Text
The Full Text of this article is available as a PDF (342.6 KB).
letter . 1997 Dec 6;315(7121):1544. doi: 10.1136/bmj.315.7121.1544
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.