RT Journal Article SR Electronic T1 Changes in FEV1 over time in COPD and the importance of spirometry reference ranges: the devil is in the detail JF Breathe JO Breathe FD European Respiratory Society SP 337 OP 339 DO 10.1183/20734735.0252-2019 VO 15 IS 4 A1 Jane Kirkby A1 Raffaella Nenna A1 Aisling McGowan YR 2019 UL http://breathe.ersjournals.com/content/15/4/337.abstract AB