Writing this book has been a rewarding but challenging experience.

Along the way I have had the helpful comments and criticisms of a number of friends and colleagues. Pat Maus, Susanna Frenkel, Kit Christensen, and Carl Ross read the entire manuscript. Steve Chilton, Milan Kovacovic, and Marina Rumyantseva read parts of it. They and the reviewers for Westview Press have weeded out many errors and forced me to think through a number of difficult points. The errors and confusions that remain do so in spite of their best efforts. I thank them all.

I would also like to thank Spencer Carr of Westview Press for his support of this project and for his editorial suggestions, which resulted in major improvements. Finally, thanks to Jean Vileta for her editorial assistance in preparing the manuscript for publication.