Dietz Vance, Venczel Linda, Izurieta Héctor, Stroh George, Zell Elizabeth R, Monterroso Edgar, Tambini Gina
Pan American Health Organization, Immunization Unit, Washington, D.C, USA.
Rev Panam Salud Publica. 2004 Dec;16(6):432-42. doi: 10.1590/s1020-49892004001200013.