Opportunities for biological nitrogen fixation in rice and other non-legumes :papers presented at the second working group meeting of the frontier project on nitrogen fixation in rice held at the National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan, 13-15 October 1996 - Bruijn, F. J. de; Ladha, J. K.; Malik, Kauser A. (Kluwer Academic Publishers, 1997)