Yee N, Markovic D, Buhr RG, Fortis S, Arjomandi M, Couper D, Anderson WH, Paine R, Woodruff PG, Han MK, Martinez FJ, Barr RG, Wells JM, Ortega VE, Hoffman EA, Kim V, Drummond MB, Bowler RP, Curtis JL, Cooper CB, Tashkin DP, Barjaktarevic IZ. Significance of FEV3/FEV6 in Recognition of Early Airway Disease in Smokers at Risk of Development of COPD: Analysis of the SPIROMICS Cohort. Chest. 2022 04; 161(4):949-959.