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\bibitem{Johansson_etal1973} {\textquotedblleft}\textit{Elemental analysis of aerosol-size fractions by proton-induced X-ray-emission}{\textquotedblright}. Johansson TB, Nelson JW, Van Grieken RE, Winchester JW, Transactions of the American Nuclear Society \textbf{17}, 103 (1973)

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