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\bibitem{Riva_etal2001} {\textquotedblleft}\textit{Positively charged magneto-excitons in a semiconductor quantum well}{\textquotedblright}. Riva C, Peeters FM, Varga K, Physical review : B : condensed matter and materials physics \textbf{64}, 235301 (2001).   http://doi.org/10.1103/PhysRevB.64.235301

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