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Francis NA, Cals JW, Butler CC, Hood K, Verheij T, Little P, Goossens H, Coenen S; GRACE Project Group.Francis NA, et al. Among authors: cals jw.Prim Care Respir J. 2012 Mar;21(1):65-70. doi: 10.4104/pcrj.2011.00083.Prim Care Respir J. 2012.PMID: 21938349Free PMC article.