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\bibitem{Zarenia_etal2011} {\textquotedblleft}\textit{Energy levels of triangular and hexagonal graphene quantum dots : a comparative study between the tight-binding and Dirac equation approach}{\textquotedblright}. Zarenia M, Chaves A, Farias GA, Peeters FM, Physical review : B : condensed matter and materials physics \textbf{84}, 245403 (2011).   http://doi.org/10.1103/PhysRevB.84.245403

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