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Burr ML, Wat D, Evans C, Dunstan FD, Doull IJ; British Thoracic Society Research Committee.Burr ML, et al.Thorax. 2006 Apr;61(4):296-9. doi: 10.1136/thx.2005.045682. Epub 2006 Jan 5.Thorax. 2006.PMID: 16396947Free PMC article.