1. J. White, Refractories J., No. 10, 414 (1966).
2. Ya. V. Klyucharov, Trudy II All-Union Conference on High-Temperature Oxide Chemistry [in Russian], Nauka (1967), p. 114.
3. V. A. Bron et al., Ogneupory, No. 1, 44 (1966).
4. A. S. Frenkel', All-Union Conference of Refractories Producers, Trudy NTO Chern. Met., Vol. 27, (no year), p. 307.
5. A. P. Panarin, Ogneupory, No. 6, 14 (1946).