1. Eastham, A. M.: Advances in Polymer Sci. 2, 18 (1960).
2. Wislicenius, J.: Ann. 192, 106 (1878).
3. Chalmers, W.: Can. J. Res. 7, 113 and 464 (1932).
4. Eley, D. D., and A. W. Richards: Research (London) 2, 147 (1949).
5. -, and J. Saunders: J. Chem. Soc. 1954, 1677, and preceding papers.