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.
Henry TJ, Pratt D.Henry TJ, et al. Among authors: pratt d.Proc Natl Acad Sci U S A. 1969 Mar;62(3):800-7. doi: 10.1073/pnas.62.3.800.Proc Natl Acad Sci U S A. 1969.PMID: 5257006Free PMC article.