1. See: Modern Theor. Chemistry, Vol. 3, Methods of electronic structure theory, edited by H.F. Schaefer III, New York: Plenum Press 1977
2. Stollhoff, G., Fulde, P.: Z. Physik B26, 257 (1977)
3. Kutzelnigg, W.: Einführung in die Theoret. Chemie, p. 207, Weinheim: Verlag Chemie 1975
4. Pauling, L.: The nature of the chemical bond, 3rd ed., p. 150, Ithaca, NY: Cornell Press 1960
5. Huzinaga, S.: Journ. Chem. Phys.42, 1293 (1965)