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.
Schumacher MC, Hunt SC, Williams RR.Schumacher MC, et al. Among authors: williams rr.Epidemiology. 1990 Jul;1(4):298-304. doi: 10.1097/00001648-199007000-00007.Epidemiology. 1990.PMID: 2083307
Williams RR, Hasstedt SJ, Wilson DE, Ash KO, Yanowitz FF, Reiber GE, Kuida H.Williams RR, et al.JAMA. 1986 Jan 10;255(2):219-24.JAMA. 1986.PMID: 3941501