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.
Bennett HS, Andres H, Pellegrino J.Bennett HS, et al.J Res Natl Inst Stand Technol. 2009 Aug 1;114(4):237-48. doi: 10.6028/jres.114.017. Print 2009 Jul-Aug.J Res Natl Inst Stand Technol. 2009.PMID: 27504225Free PMC article.