1. Knorring, O. von, and du Bois, C. G. B., Nature, 192, 1064 (1961).
2. Bailey, D. K., Ministry of Labour and Mines Geological Survey, Northern Rhodesia, Bulletin, No. 5 (1960).
3. James, T. C., Rep. Carbonatites and Rift Valleys in East Africa (Geol. Survey, Tanganyika, 1956).
4. Wyllie, P. J., and Tuttle, O. F., J. Petrol., 1, 1 (1960).
5. Wyllie, P. J., and Tuttle, O. F., Rep. Twenty-first Intern. Geol. Cong., 13, 310 (1960).