1. Herzberg, G.: Atomic Spectra and Atomic Structure, and references therein. New York: Dover Publications, inc. 1944
2. Millman, S., Kusch, P.: Phys. Rev. 60, 91 (1941) and references therein
3. Condon, E. U., Shortley, G. H.: The Theory of Atomic Spectra. Cambridge University Press 1935
4. Ref. 1, p. 51
5. Skell, P. S., Harvel, J. J., McGlinchey, M. J.: Acc. Chem. Res. 6, 97 (1973)