Population dynamics in rural areas freed from Onchocercias in West Africa : Benin (CEFORP), Burkina Faso (UERD), Cote d'Ivoire (ENSEA), Ghana (RIPS), Guinea (DNSI), Mali (DNSI), Niger (DSCN), Senegal (DPS), Togo (URD) : synthesis of national monographs - Vignikin, Kokou (Committee for International Cooperation in National Research in Demography : Ministere des Affaires Etrangeres ; Food and Agriculture Organization of the United Nations, 1999)