1. P. Nykänen-Kurki, R. Mäkelä-Kurtto, M. Mäkinen-Aakula, T. Tontti, V. Mäntylahti, Agricultural use of sludge from sewage treatment plant of the City of Mikkeli, MTT Agrifood Research Finland, Jokioinen, Finland, 2001.
2. International Standard ISO 11466, Soil quality—Extraction of trace elements soluble in aqua regia, 1995.
3. International Standard ISO 11047, Soil quality—Determination of cadmium, chromium, cobalt, copper, lead, manganese, nickel and zinc in aqua regia extracts of soil—Flame and electrothermal atomic absorption spectrometric methods, 1998.
4. Multielement graphite furnace and flame atomic absorption spectrometry;Sneddon;Adv. At. Spectrosc.,1997
5. Fast analysis with Zeeman graphite furnace AAS;Slavin;Spectrochim. Acta Part B,1989