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\bibitem{Ravindra_etal2008} {\textquotedblleft}\textit{Atmospheric polycyclic aromatic hydrocarbons: source attribution, emission factors and regulation}{\textquotedblright}. Ravindra K, Sokhi R, Van Grieken R, Atmospheric environment : an international journal \textbf{42}, 2895 (2008).   http://doi.org/10.1016/J.ATMOSENV.2007.12.010

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