The impact of using different symptom-based exacerbation algorithms in patients with COPD
J.C.A. Trappenburg, A.C. van Deventer, T. Troosters, T.J.M. Verheij, A.J.P. Schrijvers, J-W.J. Lammers, E.M. Monninkhof
European Respiratory Journal 2011; DOI: 10.1183/09031936.00130910