Special Publication 811A. Thompson and B. N. Taylor NOTE: The BIPM SI Brochure (9th Edition) was published on May 20, 2019. The NIST SP 330 2019 version has been published and reflects the changes incorporated in the BIPM SI Brochure (9th Edition). This publication, Special Publication 811, has not yet been updated to reflect the changes in the SI that came into effect on May 20, 2019 (World Metrology Day). SP 811 is a
