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.
Nápoles-Springer A, Pérez-Stable EJ, Washington E.Nápoles-Springer A, et al.J Med Syst. 1996 Oct;20(5):277-93. doi: 10.1007/BF02257041.J Med Syst. 1996.PMID: 9001995Review.