POSITIVE OPERATORS

Acknowledgments
Parts of this book were written while the authors held visiting appointments
at various institutions: California Institute of Technology, Purdue University,
the University of Southern California, and the Institute for Mathematics
and Its Applications—University of Minnesota. We express our gratitude for
the hospitality provided to us by the staffs and faculties of these institutions.
We acknowledge with many thanks the financial support we received
from the National Science Foundation under grants MCS 81–00787, MCS 82–
19750, and DMS 83–19594.
Finally, we would like to thank our wives, Bernadette and Betty, for
their assistance, and most of all for coping with our idiosyncrasies during
the difficult stages of the writing of the book.
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