1. G. Herzberg: Molecular Spectra and Molecular Structure. 1. Spectra of Diatomic Molecules, 2nd ed. ( Van Nostrand, Princeton 1950 )
2. J.C. Slater: Quantum Theory of Molecules and Solids. 1. Electronic Structure of Molecules ( McGraw-Hill, New York 1963 )
3. G. Herzberg: The Spectra and Structure of Simple Free Radicals ( Cornell University Press, Ithaca 1971 )
4. A.V. Evseev, A.A. Radzig, B.M. Smimov: Sov. Phys.-JETP 50, 283–289 (1979)
5. P.E.Cade, W.Huo: At. Data Nucl. Data Tables 12, 415 (1973); ibid 13, 339 (1974)