Sadaf, S., H. D. Durrani, and B. Bashir. “Effectiveness of Non-Invasive Vs. Invasive Ventilation in Acute Hypoxic Respiratory Failure in COVID-19 Patients in Critical Care: A Retrospective Cohort in Rahim Yar Khan, Pakistan”. Pakistan Journal of Medical Research, Vol. 60, no. 2, July 2021, pp. 90-95, https://pjmr.org.pk/index.php/pjmr/article/view/105.