1. S. R. Joshi and J. Shewchuk, Experimental Mechanics 10 (1970) 529?533.
2. L. P. Pook and K. Denton, International Journal of Fracture Mechanics 8 (1972) 118?120.
3. P. C. Paris and G. C. Sih, American Society for Testing and Materials, STP 381 (1965) 133?198.
4. For example, W. Elber, American Society for Testing and Materials, STP 486 (1971) 230?242.
5. K. Ohji, K. Ogura, and Y. Ohkubo, Proceedings of Japan - U.S. Seminar on combined nonlinear and linear (micro and macro) fracture mechanics applications to modern engineering structures, Sendai, Japan, 1 (1974) 20-1-20-15.