1. P. A. Apanasevich, Fundamentals of the Theory of Interaction between Light and Matter (Nauka i Tekhnika, Minsk, 1977) [in Russian].
2. A. I. Burshtein and A. Yu. Pusep, Sov. Phys. JETP 42(6), 978 (1975).
3. A. S. Davidov and A. A. Sericov, Phys. Status Solidi B 56, 351 (1973).
4. V. V. Samartsev, U. E. Sheibut, and U. S. Ivanov, Spectrosc. Lett. 9, 57 (1976).
5. S. N. Belkin, S. A. Moskalenko, A. Kh. Rotaru, and P. I. Khadzhi, Izv. Akad. Nauk SSSR, Ser. Fiz. 43, 355 (1979); S. N. Belkin, S. A. Moskalenko, A. Kh. Rotaru, and P. I. Khadzhi, Sov. Phys. Solid State 22 (7), 1144 (1980).