
Preface to the Fourth Edition
Another decade, another edition...
This time I have resisted the urge to tinker with the basic structure. I am grate-
ful to George Bergman, David Derbes, Peter Mulligan, Gerry Myerson, Jean Pierre
Ortolland, F. Javier Trigos-Arrieta, Hemza Yagoub, and Carlo Wood for numerous
comments, corrections, and suggestions. This edition has greatly benefited from their
advice. Known typographical errors have been corrected, though no doubt some in-
genious new ones have been introduced. Material that needed updating, such as ref-
erences, has been updated. Minor improvements to the exposition have been made
throughout.
The main changes ...