@INBOOK {EZUMAH:1990c, title = {On-farm research}, author = {Ezumah, H. C. and Mutsaers, H. J. W. }, year = {1990}, type = {Cassava in tropical Africa: a reference manual}, pages = {139--167}, publisher = {International Institute of Tropical Agriculture (IITA)}, address = {Ibadan, Nigeria}, }