1. Clouston T. W. (1938). Sudan Govt. Annual Rep. Agric. Res. Service, p. 42.
2. Crowther E. M. (1926). Sudan Govt. Rep. of a meeting in the Sudan Gezira in Dec. 1925, p. 18.
3. The dispersion of soil in water under various conditions
4. Neal J. H. (1938). Res. Bull. Mo. agric. Exp. Sta. no. 280.
5. Middleton H. E. (1930). Tech. Bull. U.S. Dep. Agric. no. 178.