1. V. V. Kaminskii, N. N. Stepanov, M. M. Kazanin, A. A. Molodykh, and S. M. Solov’ev, Fiz. Tverd. Tela 55, 991 (2012).
2. K. L. Kliewer and R. Fuchs, Phys. Rev. 185(3), 805 (1969).
3. F. Abeles, Optical properties of Metal Films. Physics of Thin Films, Ed. by M. H. Francombe and R. W. Hoffman (Academic, New York, 1971; Mir, Moscow, 1973).
4. W. E. Jones, K. L. Kliewer, and R. Fuchs, Phys. Rev. 178(3), 1201 (1969).
5. H. Kangarlou and M. Motallebi Aghgonbad, Opt. Spectrosc. 115(5), 753 (2013).