1. N. H. MacMillan, Amer. Ceram. Soc. Bull. 59 (1980) 697.
2. S. Spinner and W. E. Tefft, ASTM Proc. 61 (1961) 1221.
3. M. Griffin, MS thesis in Solid State Science, The Pennsylvania State University, 1985.
4. C. M. Preece and N. H. MacMillan, Ann. Rev. Mater. Sci. 7 (1977) 95.
5. J. Nakayama, in ?Fracture Mechanics of Ceramics?. Vol. 2: ?Microstructure, Materials and Applications?, dited by R. C. Bradt, D. P. H. Hasselman and F. F. Lange, (Plenum Press, New York, 1973) p. 759.