Efficacy and safety of direct switch to indacaterol/glycopyrronium in patients with moderate COPD: the CRYSTAL open-label randomised trial oleh Claus F. Vogelmeier, Mina Gaga, Maryam Aalamian-Mattheis, Timm Greulich, Jose M. Marin, Walter Castellani, Vincent Ninane, Stephen Lane, Xavier Nunez, Francesco Patalano, Andreas Clemens, Konstantinos Kostikas, on behalf of the CRYSTAL study investigators