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\bibitem{Xu_etal2014} {\textquotedblleft}\textit{Unusual ultra-low-frequency fluctuations in freestanding graphene}{\textquotedblright}. Xu P, Neek-Amal M, Barber SD, Schoelz JK, Ackerman ML, Thibado PM, Sadeghi A, Peeters FM, Nature communications \textbf{5}, 3720 (2014).   http://doi.org/10.1038/ncomms4720

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