Mahmood, K., I. H. naqvi, G. Ahmed, A. Mahboob, N. Baig, and M. Jumma. “SNUFFED TOBACCO MIGHTIER THAN SMOKED TOBACCO: FREQUENCY DETERMINATION OF UPPER AND LOWER RESPIRATORY TRACT DISEASES”. Pakistan Journal of Chest Medicine, vol. 21, no. 2, Sept. 2015, pp. 54-60, https://pjcm.net/index.php/pjcm/article/view/323.