1. Institute for Prevention and Cancer Epidemiology, University Medical Center FreiburgFreiburgGermany
2. Obstetrics and Gynecology Epidemiology CenterDepartment of Obstetrics, Gynecology and Reproductive BiologyBrigham and Women's HospitalHarvard Medical SchoolBostonMassachusetts
3. Department of EpidemiologyHarvard School of Public HealthBostonMassachusetts