1. Y. YAMAUCHI, S. SAKAI, M. ITO and S. ITO, Proceedings of the 27th Japan Congress on Materials Research (1984) p. 235.
2. H. P. KIRCHNER and R. M. GRUVER, “Fracture Mechanics of Ceramics 1” (Plenum, New York, 1974) p. 309.
3. O. JOHARI and N. N. PARIKH,ibid., p. 399.