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.
Elissen AM, Adams JL, Spreeuwenberg M, Duimel-Peeters IG, Spreeuwenberg C, Linden A, Vrijhoef HJ.Elissen AM, et al. Among authors: spreeuwenberg c.BMC Med Res Methodol. 2013 Mar 14;13:40. doi: 10.1186/1471-2288-13-40.BMC Med Res Methodol. 2013.PMID: 23497125Free PMC article.