Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: GOLD executive summary - Vestbo, J; Hurd, S S; Agusti, A G; Jones, P W; Vogelmeier, C; Anzueto, A; Barnes, P J; Fabbri, L M; Martinez, F J; Nishimura, M; Stockley, R A; Sin, D D; Roisin, R R (Am J Respir Crit Care Med, 2013)