1. P. Knauth and H. Tuller, J. Am. Ceram. Soc. 85(7), 1654 (2002).
2. E. I. Get’man and M. V. Mokhosoev, Neorg. Mater. 4(9), 1554 (1968).
3. J.-P. Fournier, J. Fournier, and R. Kohlmuller, Bull. Soc. Chim. Fr., No. 12, 4277 (1970).
4. E. Ya. Rode, G. V. Lysanova, and L. Z. Gokhman, Neorg. Mater. 7(11), 2101 (1971).
5. P. Lacorre, F. Goutenoire, O. Bohnke, et al., Nature 404, 856 (2000).