1. Roby, K. R.: Chem. Phys. Letters 12, 579 (1972)
2. Pople, J. A., Santry, D. P., Segal, G. A.: J. Chem. Phys. 43, S129 (1965)
3. Whitehead, M. A., Zeiss, G. D.: In Quantum chemistry: The state of the art, ed. Saunders, V. R. and Brown, J. E. D. SRC Chilton 1975
4. Zeiss, G. D.: Ph.D. Thesis, Department of Chemistry, University of McGill, 1976
5. Roby, K. R. Sinanoglu, O.: Intern. J. Quantum Chem. (Symposium) 3, 223 (1969)