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\bibitem{Brunekreef_etal2005} Brunekreef B, Janssen N A.H., de Hartog J J., Oldenwening M, Meliefste K, Hoek G, Lanki T, Timonen K L., Vallius M, Pekkanen J, Van Grieken R (2005) Personal, indoor, and outdoor exposures to PM$_{2.5}$ and its components for groups of cardiovascular patients in Amsterdam and Helsinki

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