Här anges det av IUPAC rekommenderade standardvärdet. Se: Michael E. Wieser, Tyler B. Coplen: Atomic weights of the elements 2009 (IUPAC Technical Report). In: Pure and Applied Chemistry. 2010, S.1, doi:10.1351/PAC-REP-10-09-14.
Simon MD, Geim AK (2000): Diamagnetic levitation: Flying frogs and floating magnets. Journal of Applied Physics 87, S.6200–6204 (doi:10.1063/1.372654).