1. B. Crouch, Ph.D. Thesis, University of London, Imperial College, (1986).
2. L. Dahlberg et al, Crack Arrest Methodology and Applications, ASTM STP 711 (eds. MF. Kanninen and G.T.Hahn), pp. 89, (1980).
3. J. G. Williams and A. Ivankovic, Int. J. of Fracture, (in press 1990).
4. A.S. Kobayashi et al, Int. J. of Fracture 30, pp.275, (1986).
5. P.N.R. Keegstra, Ph.D. Thesis, University of London, Imperial College, (1977).