Saima Shaheen, Maria Sarfraz, Anum Saeedullah, Nadia Qazi, Tahira Jehangir and Sara Mariyum 2022. Role of Supplementation of Vitamin C and D in their Low Serum Values in Critically Ill COPD Patients of Tertiary Care Hospital. Pakistan Journal of Chest Medicine. 28, 1 (Mar. 2022), 46–53.