AK Agarwal, and Satyendra Kumar Gahlot. “Predictors of Mortality in Acute Exacerbation of Chronic Obstructive Pulmonary Disease”. International Journal of Health and Clinical Research, vol. 5, no. 1, Jan. 2022, pp. 528-31, https://ijhcr.com/index.php/ijhcr/article/view/4650.