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.
Haidich AB, Ioannidis JP.Haidich AB, et al. Among authors: ioannidis jp.BMC Med Res Methodol. 2001;1:4. doi: 10.1186/1471-2288-1-4. Epub 2001 Jun 8.BMC Med Res Methodol. 2001.PMID: 11423002Free PMC article.