1. Dowling, J. E., and Wald, G., Proc. Fourtn Int. Cong. Biochem., 11, 185 (1960).
2. Arens, J. F., and Van Dorp, D. A., Nature, 158, 60, 622 (1946).
3. Heaton, F. W., Lowe, J. S., and Morton, R. A., Biochem. J., 67, 208 (1957). Morton, R. A., and Phillips, W. E. J., Biochem. J., 73, 416 (1959).
4. Nieman, C., and Klein Obbink, H. J., Vitam. and Horm., 12, 69 (1954).
5. Moore, T., in Symposium in Nutrition, edit. by Herriott, R. M., 55 (Johns Hopkins Press, Baltimore, 1953).