Singh, VK and Dwivedi, B S and Shukla, A K and Chauhan, Y S and Yadav, R L (2005) Diversification of rice with pigeonpea in a rice-wheat cropping system on a Typic Ustochrept: effect on soil fertility, yield and nutrient use efficiency. Field Crops Research, 92 (1). 85-105 . ISSN 0378-4290