RT Journal Article SR Electronic T1 Validated questionnaires should not be modified JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP 1015 OP 1017 DO 10.1183/09031936.00110209 VO 34 IS 5 A1 Juniper, E. F. YR 2009 UL http://erj.ersjournals.com/content/34/5/1015.abstract AB