Full Text
The Full Text of this article is available as a PDF (274.9 KB).
letter . 1999 May;5(5):618–621. doi: 10.1017/s1355838299982328
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.