1. Albrecht S.L., Gaskins H.N., Milam J.R., Schank S.C., Smith R.L.: Ecological factors affecting survival and activity ofAzospirillum in the rhizosphere, pp. 138–148 in W. Klingmukller (Ed.):Experientia Supplementum Azospirillum II, Vol. 49. Birkhäuser, Basle 1983.
2. Azcon R., Barea J.M., Hayman D.S.: Utilization of rock phosphate in alkaline soils by plants inoculated with mycorrhizal fungi and phosphate dissolving microorganism.Soil Biol. Biochem. 8, 111–115 (1975).
3. Becking J.: The familyAzotobacteriaceae, pp. 795–817 in M.P. Starr, H. Stolp, H.G. Truper, A. Balows, H.G. Schlegel:The Prokaryotes, Vol. 1. Springer-Verlag, Berlin-Heidelberg-New York 1981.
4. Bela S., Dahiya P., Lakshminarayana K.: Isolation and characterization of mutants ofAzotobacter chroococcum derepressed for nitrogenase, pp. 31–32 in R. Singh, H.S. Nainawatee, S.K. Sawhney (Eds):Current Status of Biological Nitrogen Fixation. DAE Goverment of India and Haryana Agricultural University, Hisar (India) 1986.
5. Chandna S.: Mechanism of ammonia excretion inA. chroococcum.MSc Thesis. Harayama Agricutural University, Hisar (India) 1982.