1. D. A. Bochvar and E. G. Gal’pern, Dokl. Akad. Nauk SSSR, 209, No. 3, 610 (1973).
2. A. A. Levin, Introduction to Quantum Chemistry of Solids [in Russian], Khimiya, Moscow (1974).
3. T. O. Wehling, et al., Phys. Rev. Lett., 106, 236805 (2011).
4. J. Hubbard, Proc. R. Soc., A, 276, Nо. 1365, 238 (1963).
5. G. I. Mironov and A. I. Murzashev, Phys. Solid State, 53, No. 11, 2393 (2011).