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\bibitem{Chen_etal1998} {\textquotedblleft}\textit{Voidites in polycrystalline natural diamond}{\textquotedblright}. Chen JH, Bernaerts D, Seo JW, Van Tendeloo G, Kagi H, Philosophical magazine letters \textbf{77}, 135 (1998).   http://doi.org/10.1080/095008398178561

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