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.
Braun T, Hechter O.Braun T, et al. Among authors: hechter o.Proc Natl Acad Sci U S A. 1970 Jul;66(3):995-1001. doi: 10.1073/pnas.66.3.995.Proc Natl Acad Sci U S A. 1970.PMID: 4316684Free PMC article.
Bär HP, Hechter O.Bär HP, et al. Among authors: hechter o.Proc Natl Acad Sci U S A. 1969 Jun;63(2):350-6. doi: 10.1073/pnas.63.2.350.Proc Natl Acad Sci U S A. 1969.PMID: 4308273Free PMC article.