1. S. Pearson, Engineering Fracture Mechanics, 7 (1975) 235?247.
2. W.L. Morris, Metallurgical Transactions (submitted).
3. J. Lankford, Engineering Fracture Mechanics, 9 (1977) 617?624.
4. T. Yokobori, M. Tanaka, H. Hayakawa, T. Yoshimura and S. Sasahira, Reports of the Research Institute for the Strength and Fracture of Materials, 3 (1967) 39?71.
5. T. Yokobori, H. Kuribayashi, M. Kawagishi, and N. Takeuchi, Reports of the Research Institute for the Strength and Fracture of Materials, 7 (1971) 1?23.