@ARTICLE {CARSKY:2001b, title = {Contribution of early season cowpea to late season maize in the savanna zone of West Africa}, author = {Carsky, R. and Singh, B. and Oyewole, B. }, journal = {Biological Agriculture and Horticulture}, year = {2001}, volume = {18}, pages = {303--318}, issn = {0144-8765}, }