1. De, P. K., Proc. Roy. Soc., B, 127, 121 (1939).
2. Watanabe, A., Nishigaki, S., and Konishi, C., Nature, 168, 748 (1951).
3. Soils of the Katherine Darwin Region, Northern Territory, Commonwealth Scientific and Industrial Research Organization Soil Publication No. 6, Melbourne (1950).