The authors express their great appreciation to Alberto A. Martínez and an anonymous referee for their careful reading of the manuscript and for their excellent suggestions.
We wish sincerely to thank Ruth Lewin Sime for her contribution and Gerald Holton for his advice.
We also convey our appreciation to Mihaela Barbarić of the State Archive in Zagreb, Croatia, for providing copies of the documents appearing in figures 1.1 and 1.2, and to Božidar Kereković of the State Archive for permission to publish them.
For their generous assistance in helping us locate and obtain photographs and for their permission to publish them we are very grateful to Or Orith Burla Barnea of The Albert Einstein Archives at The Hebrew University of Jerusalem; to Michael Simonson of the Leo Baeck Institute, New York; to the Niels Bohr Library and Archives, American Institute of Physics, College Park, Maryland; and to the ETH Library Zurich, Photo Archive.
The authors wish to thank Katie Helke and the staff of MIT Press for their expert work and care in the publication of this book.
In addition to the above, Allen Esterson would like to thank David C. Cassidy for his work in getting my chapters into publishable form as the first stage in the production of the final draft.