1. E. J. Underwood,Trace Elements in Human and Animal Nutrition, Academic Press, New York, 1977.
2. L. L. Hopkins, Jr, H. E. Mohr, in:New Trace Elements in Nutrition (W. Mertz, W. E. Cornatzer, eds.), Dekker, New York, 1971.
3. I. T. T. Davis,The Clinical Significance of the Essential Biological Metals, Thomas, Springfield, Ill, 1972.
4. C. R. Millican,Proc. R. Soc. Victoria 1949,61, 25.
5. A. Petrosek, E. Steven,Ind. Water Eng. 1971,10, 26.