1. Hamamura, Y., Nature, 183, 1746 (1959).
2. Hamamura, Y., and Naito, K., Nature, 190, 879 (1961).
3. Naito, K., and Hamamura, Y., J. Agric. Chem. Soc. Japan, 35, 848 (1961).
4. Hamamura, Y., Hayashiya, K., and Naito, K., Nature, 190, 880 (1961).
5. Hayashiya, K., and Hamamura, Y., J. Agric. Chem. Soc. Japan, 30, 361 (1956). Oku, M., ibid., 10, 1029 (1934).