Abstract
Full text
PDFPage 6768
. 1987 Aug 25;15(16):6768. doi: 10.1093/nar/15.16.6768
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.
