1. Division of Epidemiology, Statistics & Prevention Research, Eunice Kennedy Shriver National Institute of Child Health & Human Development, NIH, Rockville, MD
2. Texas A & M Health Science Center, School of Rural Public Health, College Station, Texas
3. Department of Epidemiology, University of North Carolina, Chapel Hill, NC
4. EMMES Corporation, Rockville, MD
5. Department of Obstetrics & Gynecology, The Ohio State University College of Medicine, Columbus, OH
6. Department of Environmental and Occupational Health, Rollins School of Public Health of Emory University, Atlanta, GA
7. Division of Applied Research and Technology, National Institute for Occupational Safety and Health, Cincinnati, OH, USA