1. Abou El-Fadl, M.et al., Nitrogen fixation by the blue-green alga,Tolypothrix tenius, as influenced by ammonium sulphate, compost, straw and superphosphate. J. Soil Sci. U.A.R. (1963).
2. Allen, O. N., Experiments in Soil Bacteriology. Burgess Pub. Co. (1961).
3. Bhattacharya, R., Growth ofAzotobacter in rice soil., Indian J. Agr. Sci.28, 73–80 (1958).
4. Elkina, O. G., Dynamics of the microbiological processes in the soil of rice fields. Mikrobiologiya6, 1239–1251 (1937).
5. Huang, D. M. and Chang, P. S., Transformation of nitrogen in paddy soils and yield of rice as affected by plowing under dry and waterlogged conditions. Acta Pedol. Sin.5, 223–233 (1957).