1. NEDECO, River Studies and Recommendations on Improvement of Rivers Niger and Benue North Holland (Amsterdam 1959).
2. Strakhov, N. M. Sovremennye osadki morei i oceanov 5–27 (Izdat. Akad. Nauk SSSR, Moscow, 1961).
3. Gibbs, R. J. Geol. Soc. Am. Bull. 78, 1203–1232 (1967).
4. Holeman, J. N. Water Resources Res. 4, 737–747 (1968).
5. Guy, H. P. & Norman, V. W. USGS Techniques of Water-Resources Investigations, Book 3, ch. C2 (1970).