Long-term triple therapy de-escalation to indacaterol/glycopyrronium in COPD patients (SUNSET): a randomized, double-blind, triple-dummy clinical trial - Chapman, KR; Hurst, JR; Frent, S; Larbig, M; Fogel, R; Guerin, T; Banerji, D; Patalano, F; Goyal, P; Pfister, P; Kostikas, K; Wedzicha, JA (American Journal of Respiratory and Critical Care Medicine, 2018)