1. Adriano, D.C. (2001)Trace elements in terrestrial environments. Springer Verlag, NewYork.
2. Allison, L.E. and Moodie, C.D. (1965) In: Black, C.A.et al. (eds),Methods of soil analysis. Agronomy, no. 9, Part 2, 2nd edn, pp. 1379–1400. ASA, Madison, WI.
3. ISO (1995). Soil quality. Extraction of trace elements soluble in aqua regia. ISO 11466, 1995(E).
4. Kersten, M. and Forstner, U. (1991) In: Batley, G.E. (ed.),Trace element speciation: Analytical methods and problems, pp. 254–317. Boca-Raton, FL: CRC Press.
5. Lindsay, W.L. (1979)Chemical equilibria soils. John Wiley and Sons New York, NY.