1. Subba Rao NS. 1980 Crop response to microbial inoculation. In: NS Subba Rao, ed, Recent Advances in Biological Nitrogen Fixation. Oxford and 1BH Publishing Co, New Delhi, Bombay, Calcutta, pp. 406–420.
2. Delwfche CC. 1970. The nitrogen cycle. In: The Biosphere. A Scientific American Book. WH Freeman and Co., San Francisco, pp. 69–80.
3. Burns RC, Hardy RWF. 1975. Nitrogen Fixation in Bacteria and Higher Plants. Springer Verlag, New York.
4. Postgate JR. 1980 Nitrogen fixation in perspective. [n:WDP Stewart and JR Gal Ion, eds, Nitrogen Fixation. Academic Press, London, pp. 423–434.
5. Delwiche CC. 1978. Legumes - past, present and future. Bioscience 28 580–585.