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Hofmann JN, Keifer MC, De Roos AJ, Fenske RA, Furlong CE, van Belle G, Checkoway H.Hofmann JN, et al.Occup Environ Med. 2010 Jun;67(6):375-86. doi: 10.1136/oem.2009.046391. Epub 2009 Oct 9.Occup Environ Med. 2010.PMID: 19819864Free PMC article.