1. Alloway, B.J. and Ayres, D.C. 1993.Chemical Principle Of Environmental Pollution, 1st edn, Blackie Academic & Professional. Glasgow.
2. ASTM (The American Society for Testing and Materials). 2001. Standard test method for major and trace elements in limestone and lime by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP) and Atomic Absorption (AAS). Designation C 1301–95. West Conshohocken. United States.
3. Jackson, M.L. 1958.Soil Chemistry Analysis. Prentice Hall, London.
4. Louekari K, Mäkelä-Kurtto, R., Pasanen, J., Virtanen, V., Sippola, J. and Malm, J. 2000.Cadmium in fertilizer. Risk to human health and the environment. Publications 4/2000. Ministry of Agriculture and Forestry. Helsinki, Finland.
5. Pasanen, J., Louekari, K. and Malm, J. 2001.Cadmium in wood ash used as fertilizer in forestry. Risk to the environment and human heath. 2001. Publications 5/2001. Ministry of Agriculture and Forestry. Helsinki, Finland.