1. G. Bertrand, Sur le role de infiniment petits elements en agriculture, C R Ville Congr. Int. Chim. Appl., New York, 28, 30–49 (1912).
2. E. J. Underwood, Trace Elements in Human and Animal Nutrition, 4th Ed., 545 pp., Academic Press, New York (1977).
3. A. I. Venchikov, Zones of display of biological and pharmacotoxicological action of trace elements, in: Trace Element Metabolism in Animals (W. G. Hoekstra et al., eds.), pp. 295–310, University Park Press, Baltimore (1974).
4. S. C. Skoryna, Y. Tanaka, Wellington Moore Jr., and J. F. Stara, Prevention of gastrointestinal absorption of excessive trace elements intake. Introductory lecture, in: Trace Substances in Environmental Health (D. D. Hemphill, ed.), pp. 3–11, University of Missouri (1973).
5. H. A. Schroeder, I. H. Tipton, and A. P. Nason, Trace metals in man: Strontium and barium, J. Chronic Dis. 25, 491–517 (1972).