Recommended values of relative atomic masses
of the elements revised biennially by the IUPAC Commission on Atomic Weights and
Isotopic Abundances and applicable to elements in any normal sample with a high level
of confidence. A normal sample is any reasonably possible source of the element or
its compounds in commerce for industry and science and has not been subject to significant
modification of isotopic composition within a geologically brief period.
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook