626 Bulletin of the World Health Organization | August 2004, 82 (8)
Reproduced by permission of the International Journal of Epidemiology
627Bulletin of the World Health Organization | August 2004, 82 (8)
628 Bulletin of the World Health Organization | August 2004, 82 (8)
629Bulletin of the World Health Organization | August 2004, 82 (8)
630 Bulletin of the World Health Organization | August 2004, 82 (8)