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\bibitem{Becker_etal1997} Becker, B., Graff, M., \& N{\"a}veke, R. (1997). Biological Treatment of Overburden from Lignite Opencast Mining in Order to Avoid Seepage of Acid Mine Water. \textit{Proceedings, 6th International Mine Water Association Congress, Bled, Slovenia}, \textit{2}, 283--291.

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