Cluster Analysis in Patients with GOLD 1 Chronic Obstructive Pulmonary Disease Gagnon, Philippe ; Casaburi, Richard ; Saey, Didier ; Porszasz, Janos ; Provencher, Steeve ; Milot, Julie ; Bourbeau, Jean ; O'Donnell, Denis E. ; Maltais, François Abstract Publication: PLoS ONE Pub Date: April 2015 DOI: 10.1371/journal.pone.0123626 Bibcode: 2015PLoSO..1023626G