ACKNOWLEDGEMENTS^5#5

First, I thank Professor James Morris, my dissertation committee chairman, for many hours of discussions and painstaking reading of many drafts. Second, I thank the other members of my dissertation committee, Professor R. S. Fabry and Professor Martin Graham. Also, I thank all of the others who have read early drafts and commented extensively, including Dr. Butler Lampson, David Redell, Dr. James Gray and Paul McJones. For typing many drafts I thank Janet Farness, and for the illustrations Carl Stewart and Jackie Southern. The Xerox Corporation has given me generous support while writing this dissertation. A generous thanks is due to a faculty member who rekindled my interests, at a time when I had become discouraged with the university, Professor R. Sherman Lehman. Finally, I thank my wife, Susan Sturgis, for her years of patience while I followed the rather tortuous path that led to this dissertation.

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