1. V. F. Suchkov et al., Electrotechnical Industry, Cable Technology Series [in Russian], Issue No. 1 (95) (1973), p. 3.
2. I. Ya. Emel'ianov et al., At. Energ.,37, No. 1, 72 (1974).
3. A. D. Neuimin and S. F. Pal'guev, in: Silicates and Oxides in High-Temperature Chemistry [in Russian], Moscow (1963), p. 253.
4. A. A. Deshkovskaya, in: Proceedings of a Conference on Physics of Insulators and Prospects for Its Development [in Russian], Vol. 1, Leningrad (1973), p. 193.
5. C. Osburn and R. J. Vest, Am. Ceram. Soc.,54, No. 9, 428 (1971).