1. C.E. Freese, quoted in [2] and [3].
2. O.L. Bowie, in Mechanics of Fracture, G.C. Sih (ed.), Vol. 1, Noordhoff International Publishing, Leyden (1973) 1?55.
3. Y. Murakami et al., Stress Intensity Factors Handbook, Pergamon Press (1986).
4. W.K. Wilson, Research Report 69?1E7-FMECH-R1, Westinghouse Research Laboratories, Pittsburgh (1969).
5. M.H. Aliabadi, D.P. Rooke and D.J. Cartwright, International Journal of Fracture 34 (1987) 131?147.