TY - JOUR T1 - COPD Challenge JF - Breathe JO - breathe SP - 73 LP - 81 VL - 4 IS - 1 AU - L. Willis Y1 - 2007/09/01 UR - http://breathe.ersjournals.com/content/4/1/73.abstract N2 - 300 Multiple ChoicesThis is a pdf-only article and there is no markup to show you.full-text.pdf ER -