C. Coelho-Oliveira, A., B. B. Monteiro-Oliveira, R. B. M. Cavalcante, D. B. Santos, A. Sonza, D. C. de Sá-Caputo, and M. Bernardo-Filho. “Vitamin D Levels and Risk of COVID-19 Infection: A Systematic Review”. Brazilian Journal of Health and Biomedical Sciences, vol. 19, no. 2, Jan. 2021, pp. 83-90, doi:10.12957/bjhbs.2020.59708.