1. D. M. Chizhikov and V. P. Schastlivyi, in: Selenium and Selenides [in Russian], Nauka, Moscow (1964), pp. 185?189.
2. S. A. Medvedev (ed.), Physics and Chemistry of AII/BVI Compounds [Russian translation], Mir, Moscow (1970), pp. 588?590.
3. F. T. Smith, Solid State Commun.,8, 263 (1970).
4. L. L. Nemenov and M. S. Sominskii, in: Fundamentals of the Physics and Technology of Semiconductors [in Russian], Nauka, Leningrad (1974).
5. S. M. Ryvkin, in: Photoelectric Effects in Semiconductors [in Russian], Fizmatgiz, Moscow (1961), pp. 132?145.