1. T. Caspersson, Skand. Archiv. f. Physiol 73, Supp. No. 8, 1936.
2. R.A. Morton, The Application of Absorption Spectra to the Study of Vitamins and Hormones, Adam Hilger, Ltd., London, 1935.
3. R.R. Williams, E.R. Buchman, and A.E. Ruehle, J. Am. Chem. Soc.
57, 1093, 1935.
4. M.M. Stimson, J. Am. Chem. Soc.
71, 1470, 1949.
5. J.R. Loofbourow and M.M. Stimson, J. Chem. Soc. (London), 1940, 844.