1. Organic carbon;Allison,1965
2. Quantification of the effect of soil organic matter content on soil productivity;Bauer;Soil Sci. Soc. Am. J.,1994
3. Integrated nutrient management in a rice–wheat system;Bhandari;J. Indian Soc. Soil Sci.,1992
4. Methods of Soil Analysis. Part 2;Black,1965
5. Determination of total, organic and available forms of phosphorus in soils;Bray;Soil Sci.,1945