Ahmad, Imran, et al. “RISK FACTORS ASSOCIATED WITH IN-HOSPITAL DEATH IN ADULT COVID-19 PATIENTS IN KARACHI, PAKISTAN: A RETROSPECTIVE CHART REVIEW”. Pakistan Armed Forces Medical Journal, vol. 70, no. 1, Aug. 2020, pp. S347-53, https://pafmj.org/PAFMJ/article/view/4931.