1. U. D. Dzhuzeev and B. G. Chernyavskii, Opt. i spektr.,20, 339, 1966.
2. I. K. Vereshchagin and L. A. Kosyachenko, Opt. i spektr., 13, 877, 1962.
3. F. F. Vol'kenshtein, Electrical Conductivity of Semiconductors [in Russian], 1949.
4. A. F. loffe, Physics of Semiconductors [in Russian], 1957.
5. U. D. Dzhuzeev and B. G. Chernyavskii, Izv. VUZ. Fizika [Soviet Physics Journal], no. 5, 12, 1967.