@INBOOK {ESIOBU:1990, title = {Nitrogen contribution of Azolla and Sesbania rostrata to rice}, author = {Esiobu, N. and Mulongoy, K. and Van Hove, C. }, year = {1990}, type = {Nitrogen fixation, achievements and objectives, edited by P.M. Gresshoff, L.E. Roth, G. Stacey, and W.E. Newton}, pages = {656}, }