1. Ph. Daniel, A. Bulou, M. Rousseau, et al., J. Phys.: Condens. Matter 2, 5663 (1990).
2. K. Rotereau, Ph. Daniel, and J. Y. Gesland, J. Phys. Chem. Solids 59, 969 (1998).
3. K. Rotereau, Ph. Daniel, A. Desert, and J. Y. Gesland, J. Phys.: Condens. Matter 10, 1431 (1998).
4. K. S. Aleksandrov, A. T. Anistratov, B. V. Beznosikov, and N. V. Fedoseeva, Phase Transitions in ABX 3 Crystals (Nauka, Novosibirsk, 1981).
5. D. Babel and A. Tressaud, in Inorganic Solid Fluorides (Academic, London, 1985), p. 77.