Handayani, E. S., R. A. Setyoningrum, and C. D. K. Wungu. “Efficacy of Vitamin D Supplementation on the Incidence of Recurrent Pneumonia in Children: A Systematic Review and Meta-Analysis Study”. International Journal of Health Sciences, vol. 6, no. S4, May 2022, pp. 2267-80, doi:10.53730/ijhs.v6nS4.7179.