1. Kh. G. Bogdanov, V. A. Golenishchev-Kutuzov, L. I. Medvedev, et al., Zh. Éksp. Teor. Fiz. 95, 613 (1989) [Sov. Phys. JETP 68, 345 (1989)].
2. D. E. Lacklison, J. Chadwik, and J. L. Page, J. Phys. D 5, 810 (1972).
3. G. B. Scott, J. Phys. D 7, 1574 (1974).
4. B. Yu. Sokolov, Fiz. Tverd. Tela (St. Petersburg) 47, 1644 (2005) [Phys. Solid State 47, 1707 (2005)].
5. A. T. Karaev, B. Yu. Sokolov, and Yu. M. Fedorov, Fiz. Tverd. Tela (St. Petersburg) 42, 2036 (2000) [Phys. Solid State 42, 2097 (2000)].