1. Pigott, K. A., Britian, J. W., Archer, W., Frye, B. F., Cote, R. J., and Saunders, J. H., Ind. Eng. Chem. Prod. Res. Develop. 7(1), 28 (1962).
2. Schollenberger, C. S., Scott, H., and Moore, G. R., Rubber World, 137, 549 (1958).
3. Saunders, J. H., and Frisch, K. C., Polyurethanes Chemistry and Technology, Part I, Inter-science Publishers, New York, p. 63 (1962).
4. Walsh, D. J. in Developments in Polyurethane—1, J. M. Buist, Ed., Applied Science Publishers Ltd., London, p. 9 (1978).
5. Reference 3, p. 44.