1. 1) R. C. Garvie, R. H. Hannink and R. T. Pascoe: Nature, 258 (1975), 703.
2. 2) A. G. Evans and A. H. Heuer: J. Am. Ceram. Soc., 63 (1981), 241.
3. 3) N. Claussen and M. Rühle: Advances in Ceramics, Vol. 3, Science and Technology of Zirconia, ed. by A. H. Heuer and L. W. Hobbs, The Am. Ceram. Soc., OH, (1981), p. 137.
4. 4) R. M. McMeeking and A. G. Evans: J. Am. Ceram. Soc., 65 (1982), 242.
5. 5) A. G. Evans: Advances in Ceramics, Vol. 12, Science and Technology of Zirconia II, ed. by N. Claussen, M. Rühle and A. H. Heuer, The Am. Ceram. Soc., OH, (1984), p. 193.