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\bibitem{Horzum_etal2013} {\textquotedblleft}\textit{Phonon softening and direct to indirect band gap crossover in strained single-layer MoSe$_{2}$}{\textquotedblright}. Horzum S, Sahin H, Cahangirov S, Cudazzo P, Rubio A, Serin T, Peeters FM, Physical review : B : condensed matter and materials physics \textbf{87}, 125415 (2013).   http://doi.org/10.1103/PhysRevB.87.125415

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