1. S. M. Lang, C. L. Fillmore andL. H. Maxwell,J. Res. Nat. Bur. Stand.
48 (1952) 298.
2. E. Kato, K. Daimon, J. Takahashi, R. Kato andK. Hamano, Report of the Research Laboratory of Engineering Materials, Tokyo Institute of Technology, No. 9 (1984) p. 75.
3. Y. Ohya, K. Hamano andZ. Nakagawa,J. Ceram. Soc. Jpn
94 (1986) 665.
4. W. R. Buessem, N. R. Thielke andR. V. Sarakauskas,Ceram. Age
60 (5) (1952) 38.
5. H. A. J. Thomas, PhD thesis, Leeds University (1988).