1. Free-living nitrogen-fixing bacteria in Egyptian soils and their possible contribution to soil fertility;Abd-El-Malek;Pl. Soil (Spec. Vol.),1971
2. Introduction to Soil Microbiology;Alexander,1977
3. Effect of different organic manures on the nitrogen content and nitrogen fractions of a sandy brown earth (Rosterde);Asmus;Thaer-Arch.,1970
4. Effect of different organic manures on the nitrogen content and nitrogen fractions of a sandy brown earth (Rosterde);Asmus;Soils Fert.,1971
5. Bekgey's Manual of Determinative Bacteriology,1974