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\bibitem{Leenaerts_etal2008} {\textquotedblleft}\textit{Graphene: a perfect nanoballoon}{\textquotedblright}. Leenaerts O, Partoens B, Peeters FM, Applied physics letters \textbf{93}, 193107 (2008).   http://doi.org/10.1063/1.3021413

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