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.
Halpern O, Holstein T.Halpern O, et al.Proc Natl Acad Sci U S A. 1942 Mar;28(3):112-8. doi: 10.1073/pnas.28.3.112.Proc Natl Acad Sci U S A. 1942.PMID: 16578031Free PMC article.No abstract available.