1. V. G. Bar’yakhtar and Yu. I. Gorobets, Fiz. Tverd. Tela (Leningrad) 18(8), 2376 (1976) [Sov. Phys. Solid State 18, 1386 (1976)].
2. A. N. Bogdanov and D. A. Yablonskii, Fiz. Tverd. Tela (Leningrad) 22(3), 680 (1980) [Sov. Phys. Solid State 22, 399 (1980)].
3. V. G. Bar’yakhtar, A. N. Bogdanov, and D. A. Yablonskii, Usp. Fiz. Nauk 156(1), 47 (1988) [Sov. Phys. Usp. 31, 810 (1988)].
4. F. V. Lisovskii, E. G. Mansvetova, and V. I. Shapovalov, Zh. Éksp. Teor. Fiz. 71(4), 1443 (1976) [Sov. Phys. JETP 44, 755 (1976)].
5. G. S. Kandaurova, L. A. Pamyatnykh, N. P. Kochneva, and A. G. Titova, Fiz. Tverd. Tela (Leningrad) 21(2), 612 (1979) [Sov. Phys. Solid State 21, 363 (1979)].