1. Lecture Notes in Chemistry,1996
2. M. I. Petrashen’, N. N. Kristoffel, and I. V. Abarenkov, Vestnik LGU No. 10, 5 (1963).
3. S. G. Semenov, Vestnik LGU No. 16, 119 (1973).
4. I. Mayer, Int. J. Quantum Chem. 29, 73 (1986).
5. R. A. Evarestov and V. A. Veryazov, Rev. Solid State Sci. 5, 415 (1991).