Young KA, Regan EA, Han MK, Lutz SM, Ragland M, Castaldi PJ, Washko GR, Cho MH, Strand M, Curran-Everett D, Beaty TH, Bowler RP, Wan ES, Lynch DA, Make BJ, Silverman EK, Crapo JD, Hokanson JE, Kinney GL. Subtypes of COPD Have Unique Distributions and Differential Risk of Mortality. Chronic Obstr Pulm Dis. 2019 Nov; 6(5):400-413.