RT Journal Article SR Electronic T1 GOLD stage I is not a COPD risk factor JF Thorax JO Thorax FD BMJ Publishing Group Ltd and British Thoracic Society SP 1107 OP 1107 VO 62 IS 12 A1 Paul L Enright YR 2007 UL http://thorax.bmj.com/content/62/12/1107.1.abstract AB