1. T. G. H. B. Boddy,Nature 54 (1943) 151.
2. B. M. Parish,J. Appl. Phys. 18 (1967) 233.
3. K. Steir andK. Schonert,Dechema-Monographien 69 (1972) Pt 1, 167.
4. H. Rumpf, Proceedings of the International Congress on Fracture, Part 1, Munich, PL1X (1973) p. 1.
5. K. E. Puttick,J. Phys. D 12 (1979) L19.