Prevalence of vitamin d deficiency and its association with recurrent respiratory infections in children: a hospital-based cross-sectional observational study. SJ Pediatrics and Child Health Africa, Africa, v. 3, n. 2, p. 8, 2026. DOI: 10.51168/pv11zr80. Disponível em: https://pediatrics.sjpublisher.org/index.php/ped/article/view/104. Acesso em: 16 aug. 2026.