- Brockwell, J., Bottomley, P.J. and Thies, J.E. 1995. Manipulation of rhizobia microflora for improving legume productivity and soil fertility: a critical assessment. Plant Soil, 174: 143-180.
- Burris, R.H., 1994. Biological nitrogen fixation past and future, p. 1-11. In N.A. Hegazi, Fayez, M. and Monib, M. (ed.), Nitrogen fixation with non-legumes. The American University in Cairo Press, Cairo, Egypt.
- Freiberg, C., Fellay, R., Bairoch, A., Broughton, W.J., Rosenthal, A. and Perret, X., 1997. Molecular basis of symbiosis between Rhizobium and legumes. Nature, 387: 394-401.
- Heidari Shariabad, H. and Dorry, M.A., 2001. Forage Crops (Leguminousae), First edition, Research Institute of Forest and Rangelands publication, Tehran, Iran.
- Mandimba, G.R., 1995. Contribution of modulated legumes on the growth of Zea mays L. under various cropping systems. Symbiosis, 19: 213-222.
- Peoples, M.B., Ladha, J.K. and Herridge, D.F., 1995. Enhancing legume N2 fixation through plant and soil management. Plant Soil, 174: 83-101.
- Sellstedt, A., Staahl, L., Mattsson, M., Jonsson, K. and Hoegberg, P., 1993. Can the 15N dilution technique be used to study N2 fixation in tropical tree symbioses as affected by water deficit J. Exp. Bot., 44: 1749-1755.
- Tate, R.L., 1995. Soil microbiology (symbiotic nitrogen fixation), John Wiley & Sons, Inc., New York, N.Y. p. 307-333.
- Viera-Vargas, M.S., Souto, C.M., Urquiaga, S. and Boddey. R.M., 1995. Quantification of the contribution of N2 fixation to tropical forage legumes and transfer to associated grass. Soil Biol. Biochem., 27: 1193-1200.
- Vincent, J.M., 1970. A manual for the practical study of root nodule bacteria. Blackwell Scientific Publications: Oxford
- Wani, S.P., Rupela, O.P. and Lee, K.K., 1995. Sustainable agriculture in the semi-arid tropics through biological nitrogen fixation in grain legumes. Plant and Soil, 174: 29-49.