Saima Shaheen, Maria Sarfraz, Anum Saeedullah, Nadia Qazi, Tahira Jehangir, and Sara Mariyum, “Role of Supplementation of Vitamin C and D in their Low Serum Values in Critically Ill COPD Patients of Tertiary Care Hospital”, Pak J Chest Med, vol. 28, no. 1, pp. 46–53, Mar. 2022.