[1] Univ San Sebastian, Revista ANACEM, Concepcion, Chile
[2] Univ Autonoma Bucaramanga, Revista MedUNAB, Com Editorial, Bucaramanga, Colombia
[3] Univ Nacl Mayor San Marcos, Revista CIMEL, Lima 14, Peru
[4] Inst Nacl Salud, Revista Peruana Med Expt & Salud Publ, Lima, Peru
[5] Cent Univ Venezuela, Journal Infect Dev Countries, Caracas, Venezuela