1. Roberts, J.D.: Molecular orbital calculations. New York: W. A. Benjamin, Inc. 1962.
2. Beveridge, D.L., Bulkin, B.J.: J. Chem. Ed. 48, 587 (1972).
3. Mooser, E., Pearson, W.B.: J. Electron. 1,1 (1956).
4. Hannay, N.B.: Solid state chemistry. Englewood Cliffs, N.J.: Prentice-Hall, Inc. 1967.
5. Zhuze, V. P.: J. Tech. Phys. Moscow 25, 2079 (1955).