A model for promoting a versatile but yet minor crop : Soybean in the farming systems of Kenya - Chianu, Jonas N.; Ohiokpehai, O.; Vanlauwe, Bernard; Okoth, Peter F.; Roing, K.; Adesina, A.A.; Naidoo, P.; Opondo, J.; Sanginga, Nteranya (International Center for Tropical Agriculture, 2007)