1. Meehan WR, Smythe LE (1967) Environ Sci Technol 1:839
2. Kabata-Pandias A, Pandias H (1984) Trace elements in soil and plants. CRC Press, Boca Raton, Florida
3. Bowen HJM (1979) Environmental chemistry of the elements. Academic Press, London Ltd
4. Merian E (1984) Metalle in der Umwelt: Verteilung, Analytik und biologische Relevanz. Verlag Chemie, Weinheim
5. Schmidt WF, Dietl F (1987) Fresenius Z Anal Chem 326:40