Sources

There are a lot of sources used on counversion.org, they can be found on page of the unit. On this page I would like to list main sources, web sites or articles about units:

• National Institute of Standards and Technology, nist.gov
• National Institute of Standards and Technology (October 2011). Butcher, Tina; Cook, Steve; Crown, Linda et al. eds. Appendix C – General Tables of Units of Measurement (link to PDF)
• National Bureau of Standards. (June 30, 1959). Refinement of values for the yard and the pound. Federal Register, viewed September 20, 2006 at National Geodetic Survey web site. (link to PDF)
• International Bureau of Weights and Measures (bipm.org)