1. Abd-el-Malek Y., Hosny I., Shawky B.T.: Studies on the aerobic non-symbiotic nitrogen-fixing bacteria, other thanAzotobacter, in Egyptian soils.Zbl. Bakt. II. Abt. 134, 507–512 (1979).
2. Anter M.A.: Microbiological studies on the rhizosphere of some desert plants.PhD Thesis. Faculty of Agriculture, Ain Shams University, Cairo (Egypt) 1976.
3. Barraquio W.L., Ladha J.K., Watanabe I.: Isolation and identification of nitrogen-fixingPseudomonas associated with wetland rice.Can. J. Microbiol. 29, 867–873 (1983).
4. Bergey's Manual of Determinative Bacteriology, 8th ed. Williams & Wilkins, Baltimore 1974.
5. Bremner J.M.: Inorganic forms of nitrogen, pp. 1179–1237 inMethods of Soil Analysis, Part 2 (C.A. Black, Ed.). American Society of Agronomy, Madison (Wisconsin) 1965.