Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Accessibility
The National Institute of Standards and Technology is committed to making its web sites accessible to all NIST customers and staff in accordance with provisions of Section 508 of the Rehabilitation Act Amendments of 1998.
If you have difficulty obtaining information from any NIST web site, or have questions, comments or suggestion for improvement, please contact 508 [at] nist.gov to get the material in another format. You should provide the URL of the web site referencing that information.