10 Acknowledgments
I am especially indebted to Michael Reisenberger, Roberto DePietri, Don Marolf, Jerzy Lewandowski,
John Baez, Thomas Thiemann, and Abhay Ashtekar for their accurate reading of the manuscript, their
detailed suggestions and criticisms. I am grateful to all my friends in the community for the joy of doing
physics together. This work was initially supported by NSF Grant PHY-95-15506. For this revision, I thank
John Baez, Jorge Pullin, and Daniele Oriti for their help, and an anonymous referee for his remarkably good
job.
