1. V. G. Litovchenko and V. I. Lyaschenko, Fiz. Tverd. Tela (Leningrad) 5(II), 3207 (1963) [Sov. Phys. Solid State 5, 2021 (1963)].
2. V. I. Lyaschenko, V. G. Litovchenko, I. I. Stepko, V. I. Strikha, and L. V. Lyaschenko, Electronic Phenomena at Semiconductor Surfaces [in Russian], Naukova Dumka, Kiev (1968).
3. V. F. Kiselev, Surface Phenomena in Semiconductors and Dielectrics [in Russian], Nauka, Moscow (1970).