1. J. J. Benbow and F. C. Roesler, Proc. Phys. Soc. B70 (1957) 201.
2. J. P. Berry, J. Polymer Sci. 50 (1961) 313.
3. E. H. Andrews, ?Fracture in Polymers? (Oliver and Boyd, London, 1968).
4. A. Van Der Boogart and C. E. Turner, Trans. & J. Plastics Inst. 31 (1963) 109.
5. G. R. Marshall, L. E. Culver, and J. G. Williams, J. Plastics Inst. 36 (1968) 75.