1. Rudy, H., in Zechmeister, L., Fortsch. Chem. organ. Naturstoffe, 2, 60 (1939).
2. Crammer, J. L., Nature, 161, 349 (1948). Consden, R., Gordon, A. H., and Martin, A. J. P., Biochem. J., 38, 224 (1944).
3. Karrer, P., Köbner, T., Salomon, H., and Zehender, F., Helv. Chim. Acta, 18, 286 (1935).
4. Karrer, P., Salomon, H., Schöpf, K., Schlittler, E., and Fritzsche, H., Helv. Chim. Acta, 17, 1010 (1934).
5. Williams, R. J., and Kirby, H., Science, 107, 481 (1948).