1. H. N. KO,J. Mater. Sci. Lett. 8 (1989) 1438.
2. Idem, ibid.,11 (1992) 1711.
3. KYOCERA, private communication.
4. R. R. MATHESON,Ceram. Age 79 (1963) 54.
5. O. JOHARI and N. N. PARIKH, in “Fracture mechanics of ceramics 1” (Plenum Press, New York, 1974) p. 399.