1. Gregory, J. W., The Rift Valleys and Geology of East Africa (Seeley Service and Co., London, 1921).
2. Fuchs, V. E., Geol. Mag., 87, 149 (1950).
3. McCall, G. J. H., Baker, B. H., and Walsh, J., Background to Evolution in Africa (edit. by Bishop, W. W., and Clark, J. D.) (University of Chicago Press, 1967).