The firs t author (Gerald W. Johnson) was supported in part by the
National Science Foundation under Grant DMS-8403197.
The second author (Michel L. Lapidus) was partially supported by a
Grant from the Faculty Research and Innovation Fund at the University
of Southern California as well as National Science Foundation Grant
DMS-8120790. He was a member of the Mathematical Sciences Research
Institut e at Berkeley and a Visiting Faculty member at the University
of Nebraska at Lincoln while much of this work was accomplished. He
would like to dedicate this memoir to his parents, Myriam and Serge
Lapidus, on the occasion of their sixtieth birthday.