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\bibitem{Ro_etal1999} {\textquotedblleft}\textit{Assessment of homogeneity of candidate reference material at the nanogram level and investigation on representativeness of single particle analysis using electron probe X-ray microanalysis}{\textquotedblright}. Ro C-U, Hoornaert S, Van Grieken R, Analytica chimica acta \textbf{389}, 151 (1999).   http://doi.org/10.1016/S0003-2670(99)00160-9

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