1. M. E. Lines and A. M. Glass, Principles and Application of Ferroelectrics and Related Materials (Clarendon, Oxford, 1977; Mir, Moscow, 1981).
2. G. A. Samara, J. Phys.: Condens. Matter 15, R367 (2003).
3. A. P. Ramirez, J. Phys.: Condens. Matter 9, 8171 (1997).
4. S. E. Park and T. R. Shrout, J. Appl. Phys. 82, 1804 (1997).
5. V. B. Shirokov and V. I. Torgashev, Kristallografiya 49, 25 (2004) [Crystallogr. Rep. 49, 20 (2004)].