Cuttle, S. P., Goodlass, G. (2004). Estimating nitrogen fixation by fertility building crops. Pages 212-215 in: Hopkins, A. (Eds). BGS Occasional Symposium 37, Organic Farming: science and practice for profitable livestock and cropping. British Grassland Society, ISBN:0905944844. Proceedings of the BGS/AAB/COR 2004 Conference, Harper Adams University College, Newport, Shropshire, UK, 20-22 April 2004.