Elberry, Ahmed A., and Abdulrahman M. Alahdal. “Relationship Between Vitamin D Deficiency and Respiratory Infection in Intensive Care Unit Patients”. World Scientific Research 3, no. 1 (December 14, 2016): 32–37. Accessed April 29, 2024. http://www.asianonlinejournals.com/index.php/WSR/article/view/751.