1. S. A. Danilkin, V. V. Zakurkin, S. I. Morozov, and V. V. Sumin, Fiz. Tverd. Tela (Leningrad) 22(11), 3327 (1980) [Sov. Phys. Solid State 22 (11), 1948 (1980)].
2. S. I. Morozov, Pis’ma Zh. Éksp. Teor. Fiz. 67(5), 326 (1998) [JETP Lett. 67 (5), 343 (1998)].
3. S. I. Morozov, V. V. Sumin, A. V. Belushkin, and I. Natkaniec, Fiz. Tverd. Tela (Leningrad) 29(6), 1653 (1987) [Sov. Phys. Solid State 29 (6), 951 (1987)].
4. S. I. Morozov and V. V. Kazarnikov, Fiz. Tverd. Tela (St. Petersburg) 35(11), 3145 (1993) [Phys. Solid State 35 (11), 1549 (1993)].
5. S. I. Morozov S. A. Danilkin, and V. T. Ém, Zh. Éksp. Teor. Fiz. 109(6), 2130 (1996) [JETP 82 (6), 1148 (1996)].