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.
The content for this page is now being maintained on https://www.nlm.nih.gov/medline/medline_policies.html#AccessPreservation
Please update your bookmarks.
Last Reviewed: February 10, 2021
