@BOOK {MANYONG:1999a, title = {Macrocharacterization of agricultural systems in West Africa; an overview: RCMP Research monograph, No. 21}, author = {Manyong, V. and Smith, J. and Weber, G. and Jagtap, S. and Oyewole, B. }, series = {RCMP Research monograph, No. 21}, year = {1999}, publisher = {International Institute of Tropical Agriculture (IITA)}, address = {Ibadan, Nigeria}, }