Yilmaz, Gulseren, et al. “Baseline Serum Vitamin A and Vitamin C Levels and Their Association With Disease Severity in COVID-19 Patients: Serum Vitamin A and C Levels and COVID-19 Severity”. Acta Biomedica Atenei Parmensis, vol. 94, no. 1, Feb. 2023, p. e2023007, https://doi.org/10.23750/abm.v94i1.13655.