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\bibitem{Smits+VanGrieken1981} {\textquotedblleft}\textit{Chelating 2,2'-diaminodiethylamine cellulose filters and X-ray fluorescence for preconcentration and trace analysis of natural waters}{\textquotedblright}. Smits J, Van Grieken R, International journal of environmental analytical chemistry \textbf{9}, 81 (1981).   http://doi.org/10.1080/03067318108071902

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