1. I. V. Murin and S. V. Chernov, Izv. Akad. Nauk SSSR, Neorg. Mater. 8, 168 (1982).
2. N. I. Sorokin, P. P. Fedorov, and B. P. Sobolev, Neorg. Mater. 33(1), 1 (1997).
3. N. I. Sorokin, I. I. Buchinskaya, and B. P. Sobolev, Zh. Neorg. Khim. 37, 2653 (1992).
4. M. Ya. Valakh, I. Kosatskii, and A. P. Litvinchuk, Sov. Phys. Solid State 28(2), 362 (1986).
5. I. Kosacki, T. Stefanski, A. P. Litvinchuk, and M. Ya. Valakh, Solid State Ionics 36, 227 (1989).