[1] Univ Bern, Inst Social & Prevent Med, Bern, Switzerland
[2] Leiden Univ, Med Ctr, Dept Clin Epidemiol, Leiden, Netherlands
[3] Univ Med Ctr, Dept Med Biometry & Med Informat, Freiburg, Germany
[4] Canc Res UK NHS Ctr Stat Med, Oxford, England
[5] Rigshosp, Nord Cochrane Ctr, DK-2100 Copenhagen, Denmark
[6] Univ Texas Hlth Sci Ctr, San Antonio, TX USA
[7] London Sch Hyg & Trop Med, Med Stat Unit, London WC1, England
[8] Univ N Carolina, Sch Publ Hlth, Dept Epidemiol, Chapel Hill, NC USA
[9] Univ Pittsburgh, Grad Sch Publ Hlth, Dept Biostat, Pittsburgh, PA 15261 USA
[10] Univ Pittsburgh, Inst Canc, Pittsburgh, PA USA
[11] Univ Bristol, Dept Social Med, Bristol, Avon, England