@MANUAL {MUTSAERS:1986, title = {A field guide for on-farm research with special reference to improvement of cropping systems and techniques in West and Central Africa}, author = {Mutsaers, H. J. W. and Fisher, M. N. * and Vogel, W. O. and Palada, M. C. }, year = {1986}, note = {On Farm Research; General; Learning Material; 177p.}, }