1. Longivity of Azotobacter;Abd-El-Malek;Plant and Soil,1966
2. Introduction to Soil Microbiology;Alexander,1976
3. Experiments in Soil Bacteriology;Allen,1959
4. Nitrogen fixation during combined cultivation of Lipomyces and bacteria;Bab'eva;Mikrobiologiya,1977
5. Comparison of the microbiology of four soils in Finnish lapland;Baker;Oikos,1974