1. L. Corry, Cohn Institute for the History and Philosophy of Science and Ideas, Tel-Aviv University, Ramat-Aviv, IL-69978 Tel-Aviv, Israel.
2. J. Renn, Max Planck Institute for the History of Science, Wilhelmstrasse 44, D-10117 Berlin, Germany.
3. J. Stachel, Boston University, Department of Physics, Boston, MA 02215, USA.