RT Journal Article SR Electronic T1 Defining airflow obstruction JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP 563 OP 564 DO 10.1183/09031936.00207014 VO 45 IS 2 A1 Margaret Smith A1 Om Kurmi YR 2015 UL http://erj.ersjournals.com/content/45/2/563.abstract AB