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\bibitem{Erten-Unal+Wixson1999} Erten-Unal, M., \& Wixson, B. G. (1999). Biotreatment and Chemical Speciation of Lead and Zinc Mine/Mill Wastewater Discharges in Missouri, USA. \textit{Water Air Soil Pollut.}, \textit{116}(3-4), 501--522.

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