1. A survey of river water quality in Northern Nigeria, with particular reference to irrigation agriculture;Bennett,1967
2. Étude pédologique du Niger oriental;Bocquier;Rapport général,1964
3. Borkou et Ounianga;Capot-Rey,1961
4. Intensity and periodicity in denudation processes with special reference to the removal of material in solution by rivers;Douglas;Z. Geomorph. N.F.,1964