1. Knoop, F., and Martins, C., Z. physiol. Chem., 258, 238 (1939).
2. Akabori, S., Ikenaka, T., and Matsumoto, K., J. Chem. Soc. Japan, Pure Chem. Sec. (Nippon Kagaku Zasshi), 73, 112 (1952).
3. Nakazaki, M., J. Chem. Soc. Japan, Pure Chem. Sec. (Nippon Kagaku Zasshi), 75, 831 (1954).
4. Maeda, G., J. Chem. Soc. Japan, Pure Chem. Sec. (Nippon Kagaku Zasshi), 77, 1011 (1956).
5. Akabori, S., Izumi, Y., and Sakurai, S., J. Chem. Soc. Japan, Pure Chem. Sec. (Nippon Kagaku Zasshi), 77, 1374 (1956).