1. Nitrogen-fixing capacity of Azotobacter as affected by the type and depth of substrate;Abd-El-Malek;Zbl. Bakt. II,1979
2. Longevity of Azotobacter;Abd-El-Malek;Plant and Soil,1966
3. Standard Methods for the Examination of Water, Sewage, and Industrial Wastes,1955
4. Nitrogen fixation capacity of Azotobacter in Siberian soils;Blinkov;Mikrobiologiya,1953
5. Estimation of bacterial densities by means of the most probable number;Cochran;Biometrics,1950