RT Journal Article SR Electronic T1 Can epidemiological studies determine the productivity-related burden of COPD? JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP 1701515 DO 10.1183/13993003.01515-2017 VO 50 IS 3 A1 Stanojevic, Sanja YR 2017 UL http://erj.ersjournals.com/content/50/3/1701515.abstract AB