1. Frank, F. C., Nature, 157, 267 (1946).
2. Rau, W., Schrift. deut. Akad. Luftfahrtforsch., 8, (ii), 65 (1944).
3. Bangham, D. H., and Razouk, R. I., Trans. Faraday Soc, 33, 1459 (1937).
4. Bangham, D. H., Fakhoury, N., and Mohamed, A. F., Proc Roy. Soc, A, 147, 152 (1934) ; 147, 175 (1934).
5. Bangham, D. H., and Saweris, Z., Trans. Faraday Soc, 34, 554 (1938).