1. Lennard-Jones, J. E., Pople, J. A.: Proc. Roy. Soc. (London) A 220, 446 (1950); A 210, 190 (1951).
2. Edmiston, C., Ruedenberg, K.: J. chem. Physics 43, 597 (1963); Rev. mod. Physics 35, 457 (1963).
3. Gilbert, T. L.: in: Molecular Orbitals in chemistry, physics and biology, p. 405, N.Y.: Acad. Press 1964.
4. Peters, D.: J. chem. Soc. (London) 1963, 2003.
5. Magnasco, V., Perico, A.: J. chem. Physics 47, 971 (1967).