RT Journal Article SR Electronic T1 Defining airflow limitation and chronic obstructive pulmonary disease: the role of outcome studies JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP 8 OP 10 DO 10.1183/09031936.00042215 VO 46 IS 1 A1 Bruce Culver YR 2015 UL http://erj.ersjournals.com/content/46/1/8.abstract AB