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Steen TW, Gyi KM, White NW, Gabosianelwe T, Ludick S, Mazonde GN, Mabongo N, Ncube M, Monare N, Ehrlich R, Schierhout G.Steen TW, et al.Occup Environ Med. 1997 Jan;54(1):19-26. doi: 10.1136/oem.54.1.19.Occup Environ Med. 1997.PMID: 9072029Free PMC article.