1. Abdou F M and El-Nennah M 1980 Plant and Soil 56, 53–57.
2. Black C A 1965 Methods of Soil Analysis. Am. Soc. Agron. Inc., Madison, Wisconsin, USA.
3. Chaney R L 1973 Crop and food chain effects of toxic elements in sludge and effluents. U.S. Environmental Protection Agency, US Dep. Agric. University Workshop. Caimpaign, Urbana, Illinois, 9–13 July 1973.
4. Ellis B G and Knezek B D 1972 Micronutrients in Agriculture, pp 59–78. Soil Sci. Soc. Am. Madison Wisconsin.
5. Friberg Let al. 1971 Cadmium in the environment. Cleveland, Ohio, Chemical Rubber Co. Press.