Both authors wish to express their gratitude to the John Simon Guggenheim Foundation for fellowship grants which assisted them in the preparation of this book. We are also grateful to the authors and publishers who generously granted permission for the reproduction of credited tabular and graphic material. All sources are cited fully in the bibliography.
Portions of the text were read critically by Jerry Hirsch and Everett R. Dempster, and many of their suggestions were adopted. However, the authors are fully responsible for all conclusions and for any errors which remain.
We are grateful to the typists, Jennie Jenkins and Helen Ehlinger, who labored over our manuscripts, and especially to Bernice Sylvester, who combined editorial surveillance with the tasks of typing and indexing. Ruth Fuller also assisted substantially with indexing and bibliographic research.
Finally, we are very appreciative of the many services and courtesies accorded to us by the publisher.
J. L. F.
W. R. T.