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\bibitem{Nowak_etal2007} {\textquotedblleft}\textit{Analysis of composite structure and primordial wood remains in petrified wood}{\textquotedblright}. Nowak J, Nowak D, Chevallier P, Lekki J, Van Grieken R, Kuczumov A, Applied spectrsocopy \textbf{61}, 889 (2007).   http://doi.org/10.1366/000370207781540141

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