H. Vannucchi, D. F. da Cunha, M. M. Bernardes, and M. R. D. L. Unamuno, “ Assessment of vitamin A, E, C and B2, carotenoid and zinc serum levels in elderly hospital patients ”, Rev. saúde pública, vol. 28, no. 2, pp. 121–126, Apr. 1994, doi: 10.1590/S0034-89101994000200005.