RT Journal Article SR Electronic T1 Combination long-acting β2-agonists and inhaled corticosteroids in chronic obstructive pulmonary disease JF Clinical Medicine JO Clin Med FD Royal College of Physicians SP 470 OP 470 DO 10.7861/clinmedicine.4-5-470a VO 4 IS 5 A1 Andrew RL Medford YR 2004 UL http://www.rcpjournals.org/content/4/5/470.2.abstract AB