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Long K, Vasquez-Garibay E, Mathewson J, de la Cabada J, DuPont H.Long K, et al.Salud Publica Mex. 1999 Jul-Aug;41(4):263-70. doi: 10.1590/s0036-36341999000400003.Salud Publica Mex. 1999.PMID: 10624137