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 provost’s office at the California In- stitute of Technology, and by the Virgle L. Hedgcoth and Susan Alexander Fund. We gratefully acknowledge grant support from the National Science Foundation and the National Endowment for the Humanities. We owe profound thanks to Barbara Wolff for her dedicated and meticulous as- sistance in proofreading numerous documents in this volume, as well as to Chaya Becker and director Roni Grosz at the Albert Einstein Archives at The Hebrew Uni- versity in Jerusalem for their sustained assistance and generous cooperation. At Caltech, we are particularly indebted to the dedicated staff of Millikan Li- brary and the Institute Archives. We thank Andrea Labinger for her careful and beautiful translations of numer- ous documents originally written in Spanish. Emily de Araujo and Alexandre Cunha kindly translated the appendixes written in Portuguese. Daniel Kennefick provided his expertise with the annotation of several documents. John Heilbron, John Norton, and Fritz Stern read the first draft and gave us significant feedback We thank Urs Schoepflin, Matthias Schwerdt, and the staff of the Max Planck Institute for the History of Science for assisting us with important literature search- es. We also thank the staff of the Swiss Federal Institute of Technology Library, the University of Zurich Archive, and Robert Schulmann for their continued assistance in examining Einstein-related materials. 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: Maria Asp, Royal Swedish Academy of Sciences Giuseppe ACKNOWLEDGMENTS