COPD in never smokers: results from the population-based burden of obstructive lung disease study. - Lamprecht B; McBurnie MA; Vollmer WM; Gudmundsson G; Welte T; Nizankowska-Mogilnicka E; Studnicka M; Bateman E; Anto JM; Burney P; Mannino DM; Buist SA; et al. (CHEST, 2011)