@INBOOK {MULONGOY:1988c, title = {Nitrogen fixation and N contribution of selected trees in alley cropping system}, author = {Mulongoy, K. and Owoaje, B. T. and Ibewiro, B. and Okogun, J. }, year = {1988}, type = {Nitrogen Fixation: hundrend years after, edited by Bothe, H.; de Bruijn, F.J.; Newton, W.E.}, pages = {824}, }