1. Allard, B., Hakansson, K., Karlsson, S. and Sigas, E. 1991. A field study of diffusion controlled migration of copper, zinc and cadmium in a clay formation. Water, Air and Soil Pollution, 57?58, 259?68.
2. Allen, S.E., Grimshaw, H.M., Parkinson, J.A. and Quarmby, C. 1974. Chemical Analysis of Ecological Materials. Blackwell Scientific Publications, Oxford.
3. Technical Monograph;B.W. Avery,1974
4. Gibb, J.P. and Cartwright, K. 1982. Retention of zinc, cadmium, copper and lead by geologic materials. Cooperative Groundwater Report No. 9, Illinois State Water Survey, Illinois State Geological Survey. pp 113.
5. Technical Report No. 87-28;E. Gustafsson,1987