1. Yu. I. Golovin, Fiz. Tverd. Tela (St. Petersburg) 46, 769 (2004) [Phys. Solid State 46, 789 (2004)].
2. M. N. Levin, V. A. Tatarintsev, O. A. Kostsova, and A. M Kostsov, Zh. Tekh. Fiz. 73(10), 85 (2003) [Tech. Phys. 48, 1304 (2003)].
3. M. N. Levin, G. V. Semenova, T. P. Sushkova, et al., Fiz. Tverd. Tela (St. Petersburg) 45, 609 (2003) [Phys. Solid State 45, 639 (2003)].
4. M. N. Levin, V. I. Belyavsky, V. V. Postnikov, et al., Ferroelectrics 307, 161 (2004).
5. V. I. Belyavsky and M. N. Levin, Phys. Rev. 70, 104101 (2004).