1. Balhausen,C.J., Gray,D.: Molecular orbital theory, p. 92. New York: Benjamin 1965
2. Pople,J.A., Santry,D.R., Segal,G.A.: J. Chem. Phys. 43, 5124 (1965); 44, 3284 (1966)
3. Pople,J.A., Beveridge,D.L.: Approximate molecular orbital theory. New York: McGraw Hill 1970
4. Messmer,R.P., Watkins,G.D.: Radiation damage and defects in semi-conductors. Inst. of Physics Conf. Series 16, 255; Phys. Rev. B 7, 2568 (1973)
5. Weigel,C., Peak,D., Corbett,J.W., Watkins,G.D., Messmer,R.P.: Phys. Rev. B 8, 2906 (1973)