Relationship between respiratory symptoms and medical treatment in exacerbations of COPD
P. Calverley, R. Pauwels, C-G. Löfdahl, K. Svensson, T. Higenbottam, L-G. Carlsson, E. Ståhl
European Respiratory Journal Sep 2005, 26 (3) 406-413; DOI: 10.1183/09031936.05.00143404