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.
Guevara JP, Wolf FM, Grum CM, Clark NM.Guevara JP, et al.BMJ. 2003 Jun 14;326(7402):1308-9. doi: 10.1136/bmj.326.7402.1308.BMJ. 2003.PMID: 12805167Free PMC article.Review.
Guevara JP, Berlin JA, Wolf FM.Guevara JP, et al.BMC Med Res Methodol. 2004 Jul 12;4:17. doi: 10.1186/1471-2288-4-17.BMC Med Res Methodol. 2004.PMID: 15248899Free PMC article.