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.
Modrow S, Wolf H.Modrow S, et al.Proc Natl Acad Sci U S A. 1986 Aug;83(15):5703-7. doi: 10.1073/pnas.83.15.5703.Proc Natl Acad Sci U S A. 1986.PMID: 3016715Free PMC article.