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\bibitem{Freire_etal2001} {\textquotedblleft}\textit{Magnetic traps for excitons in GaAs/Al$_{x}$Ga$_{1-x}$As quantum wells}{\textquotedblright}. Freire JAK, Peeters FM, Matulis A, Freire VN, Farias GA, , 503 (2001)

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