1. P. C. Paris, H. Tada, A. Zahoor and H. Ernst, ?ASTM STP 668? (American Society for Testing and Materials, Philadelphia, 1979) p. 5.
2. W. A. Spitzig, Trans. ASM 61 (1968) 344.
3. R. C. Bates and W. G. Clark, Jr, ibid. 62 (1969) 380.
4. D. harris and D. elliot, in Proceedings of the Conference on The Mechanics and Physics of Fracture, Cambridge, January 1975 (The Metals Society, 1976) p. 107.
5. H. Couque, C. P. Leung and S. J. Hudak, Jr, Engng Fract. Mech. 47 (1994) 249.