1. Division of Cancer Epidemiology and Genetics
2. DDL Diagnostic Laboratory, Voorburg, the Netherlands
3. Proyecto Epidemiológico Guanacaste, Fundación INCIENSA, Costa Rica
4. Early Detection and Prevention Section, International Agency for Research on Cancer, Lyon, France
5. Division of Cancer Prevention, National Cancer Institute, National Institutes of Health, Bethesda
6. Information Management Systems, Rockville, Maryland, USA
7. Center for Cancer Research