A. Aslam and A. Waheed, “Comparison of Forced Expiratory Volume in Six Seconds and FEV1/FEV6 ratio among Smokers and Non Smokers: FEV6 & FEV1/ FEV6 in Smokers”, J Aziz Fatm Med Den College, vol. 3, no. 1, pp. 21–24, Mar. 2021.