An official website of the United States government
The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before
sharing sensitive information, make sure you’re on a federal
government site.
The site is secure.
The https:// ensures that you are connecting to the
official website and that any information you provide is encrypted
and transmitted securely.
Paul SM, Axelrod J.Paul SM, et al. Among authors: axelrod j.Science. 1977 Aug 12;197(4304):657-9. doi: 10.1126/science.877577.Science. 1977.PMID: 877577