1. Yu. I. Golovin and R. B. Morgunov, Fiz. Tverd. Tela (St. Petersburg) 37(4), 1239 (1995) [Phys. Solid State 37, 674 (1995)].
2. Yu. I. Golovin and R. B. Morgunov, Fiz. Tverd. Tela (St. Petersburg) 37(5), 1352 (1995) [Phys. Solid State 37, 734 (1995)].
3. V. I. Al’shits, E. V. Darinskaya, and E. A. Petrzhik, Izv. Vyssh. Uchebn. Zaved., Chern. Metall., No. 10, 85 (1990).
4. V. I. Al’shits, E. V. Darinskaya, and E. A. Petrzhik, Fiz. Tverd. Tela (Leningrad) 33(10), 3001 (1991) [Sov. Phys. Solid State 33, 1694 (1991)].
5. Yu. I. Golovin and R. B. Morgunov, Zh. Éksp. Teor. Fiz. 115(2), 605 (1999) [JETP 88, 332 (1999)].