1. R. Warren andH. Matzke, in ?Science of Hard Metals?, edited by R. Viswanadham and J. Gurland (Plenum Press, New York, 1984) p. 631.
2. M. V. Swain andR. H. J. Hannink, ?Advances in Ceramics?, Vol. 12, edited by N. Claussen, M. Riihle and A. H. Heuer (American Ceramic Society, Columbus, Ohio, 1984) p. 225.
3. R. Knehans andR. Steinbrech,J. Mater. Sci. Lett. 1 (1982) 327.
4. L. M. Barker,Eng. Fract. Mech. 9 (1977) 361.
5. D. Munz, R. T. Bubsey andJ. E. Srawley,Int. J. Fract. 16 (1980) 359.