1. The Ohio State University; Division of Epidemiology; Room 324 Cunz Hall 1841 Neil Avenue Columbus Ohio USA 43210-1351
2. FHI; Clinical Sciences; P.O. Box 13950 Research Triangle Park North Carolina USA 27709
3. University of North Carolina, School of Medicine; Obstetrics and Gynecology; CB#7570 Chapel Hill North Carolina USA 27599-7570
4. FHI 360; Clinical Sciences; P.O. Box 13950 Research Triangle Park North Carolina USA 27709
5. FHI 360 and UNC School of Medicine; Quantitative Sciences; P.O. Box 13950 Research Triangle Park North Carolina USA NC 27709