1. L. Pauling,The Nature of the Chemical Bond, 3rd ed. (Cornell University, Ithaca, 1960), p. 93.
2. C. K. Jo̸laquo;Srgensen,Orbitals in Atoms and Molecules(Academic, New York, 1962), p. 94.
3. Electric polarizability, innocent ligands and spectroscopic oxidation states
4. Establishment of an optical scale for Lewis basicity in inorganic oxyacids, molten salts, and glasses
5. J. A. Duffy,Structure and Bonding, Vol. 27 (in press).