ACKNOWLEDGMENTS The editors have benefited greatly from suggestions made by John Stachel, the former editor of The Collected Papers, that helped improve this volume. We extend our thanks to the members of the Editorial Advisory Board and the Executive Committee, who discussed plans for the volume and made com- ments on the manuscript, and to Klaus Hentschel, Karl von Meyenn, Helmut Rechenberg, and Nathan Reingold, who gave it a close reading. We also wish to thank The Hebrew University of Jerusalem for granting permission to pub- lish materials from its holdings and for making the Albert Einstein Archives available to the editors. The preparation of this volume was made possible in part by grants from the National Science Foundation and from the National Endowment for the Humanities, both independent federal agencies, as well as from the Alfred P. Sloan Foundation and the Horace W. Goldsmith Foundation. Support was also provided by the following European institutional sources: the Swiss Na- tional Science Foundation, the Dr. Tomalla Foundation (Liechtenstein), the Canton of Aargau in Switzerland, and the Pieter Zeeman Foundation (The Netherlands). We are grateful to Giuseppe Castagnetti, Verena Larcher, Peter Nabholz, and Josef Poläcek, without whose assistance the documentation of much in this volume could not have been assembled. Nabholz and Larcher were in- strumental in identifying and locating material in Switzerland, Castagnetti in Berlin and in the former German Democratic Republic, and Poläcek in the li- braries and archives of Prague. Thanks are also due to Ze'ev Rosenkranz, the Bern Dibner Curator of the Albert Einstein Archives at The Hebrew Univer- sity, and to Hannah Katzenstein, who provided us with invaluable informa- tion on the original manuscripts of Einstein's unpublished papers and correspondence, as did Beat Glaus, Leiter der Wissenschaftshistorischen Sammlungen of the ETH Library, on holdings in Switzerland. The assistance of the following persons in producing this volume is also gratefully acknowledged: Christa Allert, Hechingen the late Ernst Bandi, Bern Diana Barkan, California Institute of Technology Rhoda Bilansky and the other members of the Interlibrary Loan Office at Mugar Library of Boston