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Vega-López MG, González-Pérez GJ, Muñoz de la Torre A, Valle Barbosa A, Cabrera Pivaral C, Quintero-Vega PP.Vega-López MG, et al.Cad Saude Publica. 2003 Mar-Apr;19(2):613-23. doi: 10.1590/s0102-311x2003000200028. Epub 2003 May 15.Cad Saude Publica. 2003.PMID: 12764477Free article.Spanish.