Khan B N, D. D., D. A. Dharman, D. R. Thomas, D. M. J. Hashemi, and D. S. D. Haghighi. “A Systematic Review of Covid-19 Patients With COPD As Comorbidity ”. International Journal of Medical Studies, Vol. 5, no. 9, Sept. 2020, pp. 1-10, http://ijmsonline.in/index.php/ijms/article/view/144.