1. L. M. Belyaev, V. V. Nabatov, and Yu. P. Martyshev, Kristallografiya 7(2), 576 (1962) [Sov. Phys. Crystallogr. 7, 461 (1962)].
2. V. M. Finkel’, Yu. I. Tyalin, Yu. I. Golovin, et al., Fiz. Tverd. Tela (Leningrad) 21, 1943 (1979) [Sov. Phys. Solid State 21, 1116 (1979)].
3. Yu. I. Golovin and A. A. Shibkov, Fiz. Tverd. Tela (Leningrad) 28, 3492 (1986) [Sov. Phys. Solid State 28, 1964 (1986)].
4. Yu. I. Golovin and A. A. Shibkov, Kristallografiya 35(2), 440 (1990) [Sov. Phys. Crystallogr. 35, 254 (1990)].
5. Yu. I. Golovin, T. P. D’yachek, and V. M. Dolgova, Fiz. Tverd. Tela (Leningrad) 28, 2502 (1986) [Sov. Phys. Solid State 28, 1400 (1986)].