1. Division of Epidemiology, Statistics, and Prevention Research; Eunice Kennedy Shriver National Institute of Child Health and Human Development; National Institutes of Health; Department of Health and Human Services; Bethesda; MD
2. Division of Genetics, Wadsworth Center; New York State Department of Health; Albany; New York
3. Department of Epidemiology; The University of Iowa College of Public Health; Iowa City; Iowa; USA
4. Genome Technology Branch; National Human Genome Research Institute; National Institutes of Health; Bethesda; MD