In order to offer broad coverage of theories, approaches, and topics in this volume, each contribution has been edited down to approximately two-thirds of its originally published length. The authors of each contribution actively supported this endeavor.

While citations within articles have been maintained, complete references have been omitted from the book. However, a complete set of references for each of the chapters in the book may be found at http//:www.cambridge.org/9780521861861.

The deletion of originally published text is signified in this book by the insertion of asterisks. Where three asterisks appear within or at the end of a paragraph, part of the originally published paragraph has been deleted. Where three asterisks appear between paragraphs, one or more paragraphs have been removed. A single asterisk marks where a footnote was deleted. Text appearing within brackets signifies that those words have been changed from the originally published article or added during the editing process. Neither asterisks nor brackets appear in Chapter 4, which was substantially revised from the original by one of its co-authors.