Cover crops for natural resource management in West Africa=Plantes de couverture et gestion des ressources naturelles en Afrique occidentale: proceedings of a workshop organized by IITA and CIEPCA, Cotonou, Benin, 2629 October 1999 - Carsky, R.J.; Eteka, A.; Keatinge, J.D.H.; Manyong, Victor M. (2000)