RT Journal Article SR Electronic T1 A theory explaining time trends in asthma prevalence JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP 434 OP 435 DO 10.1183/09031936.06.00119105 VO 27 IS 2 A1 D. L. Hahn YR 2006 UL http://erj.ersjournals.com/content/27/2/434.2.abstract AB