1. Cotzias, G. C. 1967.Trace Substances in Environmental Health, Edited by: Hemphill, D. D. 5Columbia: University of Missouri.
2. Schwarz, K. 1974.Trace Element Metabolism in Animals – 2, Edited by: Hoekstra, W. G., Suttie, J. W., Ganther, H. E. and Mertz, W. 355Baltimore: University Park Press.
3. Mertz, W. 1977. Symp. on Ultratrace Metal Analysis in Biological Sciences and Environment. 1977, Chicago. American Chemical Society