1. A. Majdic and Routschka, Keram. Z.,23, No. 10, 583?591 (1971).
2. N. V. Pitak, S. A. Antonov, and T. A. Anisimova, Ogneupory, No. 10, 38?44 (1974).
3. V. V. Primachenko, T. A. Zadorozhnaya, and M. E. Drizheruk, Ogneupory, No. 10, 38?44 (1976).
4. S. P. Shmitt-Fogelevich, Ogneupory, No. 12, 49?56 (1968).
5. L. B. Borovkova, E. S. Lukin, and D. N. Poluboyarinov, Ogneupory, No. 6, 27?30 (1971).