1. Contraceptive Use and Epidemiology Division, Family Health International, Research Triangle Park, NC 27709, USA
2. Formerly with the Program Evaluation Division, Family Health International, Research Triangle Park, NC 27709, USA
3. Biostatistics Division, Family Health International, Research Triangle Park, NC 27709, USA
4. Formerly with the Materials Technology Division, Family Health International, Research Triangle Park, NC 27709, USA