1. 1) W. Weibull, Ingevetenskakad Hadl., No. 151, Stockholm (1939).
2. 2) Y. Yokobori, The Strength of Materials, Iwanami Press, Tokyo (1974). (in Japanese)
3. 3) S. M. Wiederhorn and L. H. Bolz, J. Ceram. Soc. Am., 53 (1974) 543.
4. 4) A. G. Evans and K. T. Faber, J. Am. Ceram. Soc., 67 (1984) 255.
5. 5) H. L. Oh and I. Finnie, Int. J. Fracture, 6 (1970) 287.