The content is available as a PDF (343.0 KB).
. 2001 Nov;52(5):615–627. doi: 10.1046/j.1365-2125.2001.00525.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.