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\bibitem{Zhang_etal2009} {\textquotedblleft}\textit{Resonant tunneling through S- and U-shaped graphene nanoribbons}{\textquotedblright}. Zhang ZZ, Wu ZH, Chang K, Peeters FM, Nanotechnology \textbf{20}, 415203 (2009).   http://doi.org/10.1088/0957-4484/20/41/415203

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