1. Isupov, V.A, Phys. Solid State, 2003, vol. 45, no. 6, p. 1107.
2. Vugmeister, B.E. and Glinchuk, M.D., J. Exp. Theor. Phys., 1980, vol. 52, no. 3, p. 482.
3. Vugmeister, B.E. and Glinchuk, M.D., Phys.—Usp., 1985, vol. 28, no. 7, p. 589.
4. Stukova, E.V. and Baryshnikov, S.V., Inorg. Mater., 2011, vol. 2, no. 5, p. 434.
5. Stukova, E. and Baryshnikov, S., Perspekt. Mater., 2011, no. 13, p. 801.