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.
This page is no longer being maintained.
The content can be found on https://wayback.archive-it.org/org-350/20240307194926/https://www.nlm.nih.gov/nichsr/hta101/ta10104.html
This page will be deleted on 5/13/2025.
Last Reviewed: November 21, 2019
