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Bulletin of the World Health Organization 1984;62(5):749-53 301Bulletin of the World Health Organization 2003, 81 (4) 302 Bulletin of the World Health Organization 2003, 81 (4) 303Bulletin of the World Health Organization 2003, 81 (4) 304 Bulletin of the World Health Organization 2003, 81 (4) 305Bulletin of the World Health Organization 2003, 81 (4)