1. C. E. Hartbower, ASTM, STP, 466.
2. P. I. Vincent, Plastics Institute Monograph (1971).
3. G. R. Irwin,Appl. Mats. Res 3 April (1964) p. 65.
4. H. F. Brown andJ. E. Srawley, ASTM, STP, 410 (1966).
5. B. Cotterell,Appl. Mats. Res. 4 Oct. (1965) p. 227.