RT Journal Article SR Electronic T1 Socioeconomic status and chronic obstructive pulmonary disease JF Thorax JO Thorax FD BMJ Publishing Group Ltd and British Thoracic Society SP 737 OP 741 DO 10.1136/thx.54.8.737 VO 54 IS 8 A1 Eva Prescott A1 Jørgen Vestbo YR 1999 UL http://thorax.bmj.com/content/54/8/737.abstract AB