1. Professor of Pathology, The George Washington University, Medical Center, Washington, D.C., U.S.A.
2. Associate Director, Division of Clinical Oncology G, Istituto Nazionale per lo Studio e la Cura dei Tumori, Milan, Italy
3. Pathologist, Het Nederlands Kankerinstituut Amsterdam, The Netherlands
4. Statistician, Istituto Nazionale per lo Studio e la Cura dei Tumori, Milan, Italy
5. Cancer Research Centre of the U.S.S.R. Academy of Medical Sciences, Moscow, U.S.S.R.
6. Istituto Nazionale per lo Studio e la Cura dei Tumori « Fondazione Pascale », Naples, Italy
7. Herzen State Oncological Institute, Moscow, U.S.S.R.
8. Het Nederlands Kankerinstituut, Amsterdam, The Netherlands
9. Hospital A. C. Camargo, Sao Paolo, Brazil; Head of the Department of Pathologists, Instituto Nacional de Enfermedades Neoplasticas, Lima, Perù
10. Institut Gustave Roussy, Villejuif, France
11. Institut Jules Bordet, Brussels, Belgium
12. Istituto Nazionale per lo Studio e la Cura dei Tumori, Milan, Italy
13. Norwegian Radium Hospital, Oslo, Norway
14. Oncological Research Institute, Sofia, Bulgaria
15. Oncological Institute, Cracow, Poland
16. Oncological Institute, Gliwice, Poland
17. Oncological Institute, Warsaw, Poland
18. Oncological Institute, Brno, Czechoslovakia
19. Petrov Research Institute of Oncology, Leningrad, U.S.S.R.
20. State Institute of Oncology, Budapest, Hungary.