1. Alexander, M. 1961 Introduction to Soil Microbiology, John Wiley and Sons, New York, 293 p.
2. Alexander, M. 1965 Nitrification.In Soil Nitrogen. Eds. W. V. Bartholomew and F. E. Clark. Am. Soc. Agron. Inc., U.S.A. pp 307–343.
3. Amer, F. M. and Bartholomew, W. V. 1951 Influence of oxygen concentration in soil air on nitrification. Soil Sci.71, 215–219.
4. Asami, T. and Takai Y. 1963 Formation of methyl mercaptan in paddy field. Soil Sci. Plant Nutr.9, 65–69.
5. Bremner, J. M. 1965 Inorganic forms of nitrogen.In Methods of Soil Analysis. Ed. C. A. Black. Am. Soc. Agron. Inc. U.S.A. pp 1179–1237.