1. Harris, G. M., and M. Weissbluth: Physic. Rev. 149, 198 (1966).
2. ?: Theoret. chim. Acta (Berl.) 5, 379 (1966).
3. Richards, L., W. S. Caughey, H. Eberspaecher, G. Feher, and M. Malley: J. Chem. Physics (in press).
4. Harris, G. M.: J. Chem. Physics (in press).
5. Griffith, J.: The theory of transition metal ions. Cambridge (England): Cambridge University Press 1961.