The editors have benefited greatly from the assistance of many individuals and institutions. We extend our thanks to the members of the Executive Committee, and wish to thank The Hebrew University of Jerusalem for granting us permission to publish materials from its holdings. The ongoing support of the Harold McGraw, Jr., endowment is deeply appreci- ated. Generous assistance was provided by the California Institute of Technology and by the Virgle L. Hedgcoth and Susan Alexander Fund. We gratefully acknowledge grant support from the National Science Foundation. We thank Chaya Becker and director Roni Grosz at the Albert Einstein Archives at The Hebrew University in Jerusalem for their sustained assistance and generous cooperation. We also thank Nurit Lifshitz for her conscientious archival and news- paper research. Many thanks to John L. Heilbron and John D. Norton for helpful editorial sug- gestions. We thank Matthias Schwerdt and the staff of the Max Planck Institute for the History of Science in Berlin for assisting us with important literature searches. At the California Institute of Technology, we have received encouragement and support from David Tirell, the Provost, and from the chair of the Division of the Humanities & Social Sciences, J.-L. Rosenthal. Important research and editorial assistance was provided by Caltech students Madison Lee and Maggie Anderson. We also thank our graduate student collaborators Melissa Büttner, Mara Julseth, Jeremy Schneider, and Tobias Schütz. Much detailed historical information was needed in the scholarly annotation of the documents presented in this volume. We gratefully thank the following persons for their assistance: Birgit Ahrens, Hamburg Christoph Albers, Staatsbibliothek Berlin Evamarie Bange, Luxembourg City Archives Anat Banin, Central Zionist Archives, Jerusalem Yochai Ben-Ghedalia, Central Archives for the History of the Jewish People, Jerusalem Valentin Borodin, Moscow Gene Dannen, Corvallis Jude Davies, Theodor Dreiser Papers, University of Winchester, United Kingdom Michael DiRuggerio, Manhattan Rare Books, New York Simon Ertz, Hoover ACKNOWLEDGMENTS