1. Department of Hygiene and Epidemiology, University of Athens Medical School, Athens, Greece
2. Unit of Analytical Epidemiology, International Agency for Research on Cancer, Lyon, France
3. D. Trichopoulos, Department of Epidemiology, Harvard School of Public Health, Boston, Mass., U.S.A., Address for reprints: D. Trichopoulos Harvard School of Public Health Department of Epidemiology 677 Huntington Avenue Boston, MA 02115, U.S.A.