Kumar, P and Joshi, P K and Johansen, C and Asokan, M  (2000) Total factor productivity of rice-wheat cropping systems in India - the role of legumes.   In:  Legumes in rice and wheat cropping systems of the Indo-Gangetic Plain - constraints and opportunities.   International Crops Research Institute for the Semi-Arid Tropics, Patancheru, Andhra Pradesh, India, pp. 166-175.  ISBN 92-9066-418-5