1. Ahmad, N.: 1983, ?Vertisols?, in L. P. Wilding, N. E. Smeck, and G. F. Hall (eds.), Pedogenesis and Soil Taxonomy: II. Soil Orders. Developments in Soil Science 11A, Elsevier Science Publishers, The Netherlands.
2. R10-MB-77;E. B. Alexander,1989
3. Allen, B. L. and Fanning, D. S.: 1983, ?Composition and Soil Genesis?, in L. P. Wilding, N. E. Smeck, and G. F. Hall (eds.), Pedogenesis and Soil Taxonomy: I. Concepts and Interactions. Developments in Soil Science 11A, Elsevier Science Publishers, The Netherlands.
4. Allison, F. E.: 1973, Soil Organic Matter and Its Role in Crop Production, Elsevier Scientific Publishing Co., N.Y.
5. Amundson, R. G. and Davidson, E. A.: 1990, J. Geochem. Explor. 38, 13.