1. Yoffe, E. H.,Phil. Mag. 42 (Pt 2), 739 (1951).
2. Craggs, J. W., J. Mech. Phys. Solids, 8, 66 (1960).
3. Baker, B. R., J. Mech. Appl. Mech., 29, 449 (1962).
4. Broberg, K. B., Arkiv. für Fysik, 18 (No. 10), 159 (1960).
5. Rice, J. R., In Fracture II (ed. H. Liebowitz), ch. 3, p. 236. Academic Press, New York and London (1968).