1. M. E. Lines and A. M. Glass: “Principles and Applications of Ferroelectrics and Related Materials”, Clarendon Press, Oxford, 1977
2. R. A. Cowley, Adv. Phys. 29, 1 (1980); A. D. Bruce, ibid., Adv. Phys. p. 111
3. A. D. Bruce and R. A. Cowley, Adv. Phys. 29, 219 (1980)
4. H. Kawamura, in: Physics of Narrow Gap Semiconductors, ed. by J. Rauluszkiewicz e.a. (PWN, Polish Scientific Publishers Warszawa 1978) p. 7, and in: “Narrow Gap Semiconductors”, ed. by W. Zawadzki, Lecture Notes in Physics 133, 470 (1980)
5. K. Murase, J. Phys. Soc. Japan, 49, Suppl. A, 725 (1980)