Salako, F.K., F.A. Olowokere, G. Tian, G. Kirchhof, and O. Osiname. 2007. “Ground Cover by Three Crops Cultivated on Marginal Lands in Southwestern Nigeria and Implications for Soil Erosion”. Spanish Journal of Agricultural Research 5 (4), 497-505. https://doi.org/10.5424/sjar/2007054-272.