c v i A C K N O W L E D G M E N T S Berlin-Brandenburgischen Akademie der Wissenschaften, Berlin Hanoch Gutfreund, Hebrew University of Jerusalem Sophie Hoffmann, Universitäts- und Landesbibliothek Münster Beata M. Jelinek, National Geophysical Library, Buda- pest Martin Kröger, Politisches Archiv des Auswärtigen Amts, Berlin Hans-Josef Küpper, Cologne Benedikt Marchand, Deutsches Museum, Munich Susan Marti, Bernisches Historisches Museum, Bern Ya’akov Mazurek, Jerusalem Cornelia F. Mutel, University of Iowa, Iowa City Hans Muggli, Niederlenz, Switzerland Sanjib Mukhopadhyay, Kolkata Jacques Oberson, League of Nations Archives, Geneva Ádám Parti, Library of the Parliament, Budapest Stefanie Peters, Univer- sitäts- und Landesbibliothek Münster Tully Potter, Hildenborough, United King- dom Alexander Riepenhausen, Deutsches Museum, Munich Franziska Rogger, Hinterkappelen, Switzerland Roland Schmidt-Hensel, Music Department, Staats- bibliothek Berlin Jutta Schöffel, Staatsbibliothek Berlin Michael Simonson, Leo Baeck Institute, New York Anke Spille, Zentral- und Landesbibliothek Berlin Jim Stasheff, University of Pennsylvania Barbara Studer Immenhauser, Staatsarchiv Bern Emilie TČsínská, ß Institute for Contemporary History, Prague Alexandra Vlachos, Bernisches Historisches Museum, Bern Marie-Laure Wagner, Paris Joe Weber, American Jewish Archives, Cincinnati Patrick Wild, Egg, Switzerland Gabriele Wohlgemuth, Zentralbibliothek Zürich. Loma Karklins and Elisa Piccio of the Caltech Institute Archives have been gen- erous in their help with archival documents and rare books. Intensive work has been carried out at the Einstein Papers Project by talented and dedicated students. We thank Melissa Büttner, Kalyn Chang, Ella Jacoby, Mara Julseth, Jeremy Schneider, Claus Spenninger, and Thea Wade. Our activities and well-being at Caltech have been furthered by the assistance of Jean-Laurent Rosenthal and Ed Stolper, as well as Jey Giuliano, Tiffany Kim, Gail Nash, Candace Younger, and many other colleagues. Many thanks to everyone at Princeton University Press, especially to Terri O’Prey and Leslie Flis, our production team Beth Gianfagna, the painstaking copy editor Neil Litt Adam Fortgang and Martha Camp. We also thank Al Bertrand and Kenneth Reed for their dedication to making Einstein’s writings available in print and online. We owe a profound debt of gratitude to Peter Dougherty, Director of Princeton University Press from 2005 to 2017. The Einstein Papers Project has flourished un- der his visionary and caring leadership. We dedicate this volume to the memory of Fritz Stern, distinguished and prolific historian, who served for many decades on the Executive Committee of the Ein- stein Papers Project and contributed fundamental insights to our understanding of Einstein’s Germany.