Vitamin A deficiency in adolescents served in a health care facility in Ribeirão Preto city (SP) - Ferraz, Ivan Savioli; Daneluzzi, Julio Cesar; Ciampo, Luiz Antonio Del; Jordão Júnior, Alceu Afonso; Souza, Cristiane Simões Bento de; Vannucchi, Hélio (Reunión de la Sociedad Latinoamericana de Investigación Pediátrica, 2011)