Meija, Juris; Coplen, Tyler B.; Berglund, Michael; Brand, Willi A.; De Bièvre, Paul; Gröning, Manfred; Holden, Norman E.; Irrgeher, Johanna et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry 88 (3): 265–91. doi:10.1515/pac-2015-0305.  Berger, Dan. "Why does Tungsten not 'Kick' up an electron from the s sublevel ?". Bluffton College, USA.  Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press. "Why does Tungsten not 'Kick' up an electron from the s sublevel ?". Retrieved 2008-06-15.