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.
[Bethesda, Md.] : Health, Education, and Welfare, Public Health Service, National Institutes of Health, National Library of Medicine ; [Washington : for sale by National Audiovisual Center], 1979