1. A. G. Karaulov et al., Izv. Akad. Nauk SSSR, Neorg. Mater.,3, 6 (1967).
2. A. G. King and P. I. Jaworsky, J. Amer. Cer. Soc., No. 1 (1968).
3. G. A. Gogotsi, A. G. Gashchenko, and A. A. Kurashevskii, Probl. Prochnosti, No. 4 (1972).
4. G. A. Gogotsi, A. G. Gashchenko, et al., Ogneupory, No. 1 (1973).
5. B. A. Drozdovskii (editor), Applied Problems of Fracture Toughness [Russian translation], Mir, Moscow (1968).