1. I. M. Ward, “Mechanical Properties of Solid Polymers” (Wiley, London, 1971) p. 229.
2. I. Wilson, A. Cunningham andI. M. Ward,J. Mater. Sci. 11 (1976) 2188.
3. I. Wilson, N. H. Ladizesky andI. M. Ward,ibid 11 (1976) 2177.
4. A. H. Cottrell, “The Mechanical Properties of Matter” (Wiley, London, 1964) p. 335.
5. D. A. Thomas,Plastics and Polymers 37 (1969) 485.