1. Soil factors affecting rainfel agriculture in semi-arid regions with particular reference to the Sahel Zone of Africa;Ahn,1977
2. Properties of tied ridges in the Sudan Savannah of The West Semi-arid Tropics;Hulugalle,1988
3. Land forming effects on dry-land sorghum production in the Southern Great Plains;Jones;Soil Sci. Soc. Am. Pro.,1981