1. M. Schnitzer, S. U. Khan, Humic Substances in the Environment, Marcel Dekker, New York, 1972, Chapter 6.
2. F. J. Stevenson, Humus Chemistry: Genesis, Composition, Reactions, John Wiley & Sons, New York, 1982, Chapter 15.
3. P. MacCarthy, E. M., Perdue, Interactions at the Soil Colloid-Soil Solution Interface,C.H. Bolt et al. (Eds), Kluwer, The Netherlands, 1991, Chapter 13.
4. Z. Y. Tao, J. Z. Du, Radiochim. Acta, 64, (1994) 225.
5. Z. Y. Tao, H. X. Gao, Radiochim. Acta, 65 (1994) 121.