1. D.L. Chen, B. Weiss and R. Stickler, International Journal of Fracture 55 (1992) R3.
2. H. Tada, P. Paris and G. Irwin, The Stress Analysis of Cracks Handbook, Del Research Corporation, Hellertown, Pennsylvania (1973) 2.22?2.23 and 5.9?5.10.
3. H.M. Westergaard, Journal of Applied Mechanics 61 (1939) 49?53.
4. J.F. Knott, Fundamentals of Fracture Mechanics, 3rd ed, Butterworth & Co., London (1979) 53?65.