1. Department of Epidemiology and Cancer Control; St. Jude Children's Research Hospital; Memphis Tennessee
2. Center for Outcomes Research; JPS Health Network; Fort Worth Texas
3. Department of Hematology; Aarhus University Hospital; Aarhus Denmark
4. Department of Public Health; Erasmus Medical Center; Rotterdam The Netherlands
5. Department of Medical Statistics and Bioinformatics; Leiden University Medical Center; Leiden The Netherlands
6. Department of Pediatrics; Aarhus University Hospital; Aarhus Denmark