1. G. Del Re, J. Ladik, and C. Biczo,Phys. Rev. 155, 967 (1967); J.-M. Andre, L. Gouverneur, and G. Leroy,Int. J. Quantum Chem. 1, 427,451 (1967); R. N. Euwema, D. L. Wilhite, and G. T. Surrat,Phys. Rev. B7, 818 (1973).
2. J. Ladik, in:Electronic Structure of Polymers and Molecular Crystals(J.-M. Andre and J. Ladik, eds.), p. 23, Plenum Press, New York-London (1975).
3. G. Biczo, unpublished result.
4. J. Ladik and J. Cizek,Int. J. Quantum Chem. (submitted).
5. 3. I.I. Ukrainski,Theor. Chim. Acta30, 139 (1975)