The list of those to whom I am indebted is a long one. Prof. Neil Wallace (University of Minnesota) stimulated my interest in the kind of models with which the book deals. I am grateful for a large number of conversations with him. I learned a lot from him and will always be proud that I have been one of his student. I hope that he is not dissappointed with the outcome. I am deeply indebted to Prof. Dr. Hans-Werner Sinn (University of Munich). His observations and critical remarks were instrumental for a great number of changes and improvements which I was able to introduce while revising the manuscript again and again, and rethinking the basic arguments. I also want to thank Prof. Dr. Utta Gruber (University of Munich) for her helpful comments and for her support. I am very much obliged to Prof. Dr. Dr. h. c. Hans Moller (University of Munich). For many years I have had the honour of a nearly continuous dialogue with him. I am also grateful to Prof. Dr. Werner Gumpel (University). The stimulating atmosphere and the research opportunities which were provided by his seminar contributed a lot to my work. Finally I want to thank my wife Sigrid for looking through the English draft of this book and correcting numerous linguistic flaws. The remaining errors are of course mine. CONTENTS Page v Preface 1. INTRODUCTION 1. 1.

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