Verma, L., H. Borana, G. Desai, and S. Tak. “Saber Sheath Trachea in Chronic Obstructive Pulmonary Disease Patients”. International Journal of Advances in Medicine, vol. 6, no. 3, May 2019, pp. 989-90, doi:10.18203/2349-3933.ijam20192278.