Effect of flucticasone propionate/ salmetrerol (250/50) on COPD exacerbations and impact on patient outcomes - Anzueto, A; Ferguson, GT; Feldman, G; Chinsky, K; Seibert, A; Emmett, A; Knobil, K; O’Dell, D; Kalberg, C; Crater, G (Journal of Chronic Obstructive Pulmonary Disease, 2009)