1. Shashoua, V. E., Sweeny, W., Tietz, R. F, J. Am. Chem. Soc., 82, 866 (1960).
2. Nicholas, L., and Gmitter, G. R., J. Cellular Plast. 1, 85 (1965).
3. Sayigh, A. A. R., Advances in Urethane Science and Technology, Vol. III, 141 (1974), Technomic Publishing Co., Westport, CT.
4. Nawata, T., Kresta, J. E., and Frisch, K. C., J. Cellular Plast. 11, 267 (1975).
5. Frisch, K. C., and Kresta, J. E., International Progress in Urethanes, Vol. 1, 191 (1977), Technomic Publishing Co., Westport, CT.