1. V. V. Bryksin and Yu. A. Firsov, Zh. Éksp. Teor. Fiz. 61, 2373 (1971) [Sov. Phys. JETP 34, 1272 (1972)].
2. V. V. Bryxin and Yu. A. Firsov, Solid State Commun. 10, 471 (1972).
3. V. V. Bryksin, Fiz. Tverd. Tela (Leningrad) 14, 802 (1972) [Sov. Phys. Solid State 14, 684 (1972)].
4. V. V. Pavlovich and É. M. Épshteĭn, Fiz. Tverd. Tela (Leningrad) 18, 1483 (1976) [Sov. Phys. Solid State 18, 863 (1976)].
5. V. V. Pavlovich and É. M. Épshteĭn, Fiz. Tekh. Poluprovodn. (Leningrad) 10, 2001 (1976) [Sov. Phys. Semicond. 10, 1196 (1976)].