1. L. Pauling, The Nature of the Chemical Bond [Russian translation], 3rd ed., Cornell University Press, Ithaca (1960).
2. Ya. K. Syrkin, Uspekhi Khim.,31, 397 (1962).
3. V. M. Koshkin, Ukr. Fiz. Zh.,9, 973 (1964); V. M. Koshkin, Yu. F, Komnik, and S. D. Orlova, in Coll: The Chemical Bond in Semiconductors and Solid Bodies [in Russian], ?Nauka i tekhnika? Minsk (1965), p. 304.
4. Zh. P. Syushe, The Physical Chemistry of Semiconductors [in Russian], ?Metallurgiya,? Moscow (1964).
5. M. V. Fok, Fiz. Tverd. Tela.,5, 1493 (1963).