Arbillaga-Etxarri A, Gimeno-Santos E, Barberan-Garcia A, Benet M, Borrell E, Dadvand P, Foraster M, Marin A, Monteagudo M, Rodriguez-Roisin R, Vall-Casas P, Vilaro J, Garcia-Aymerich J. Socio-environmental correlates of physical activity in patients with chronic obstructive pulmonary disease (COPD). Thorax. 2017 Sep;72(9):796-802. doi: 10.1136/thoraxjnl-2016-209209