This series is devoted to the publication of Seminar Notes and Conference Proceedings which contain mainly original contributions written in their final form. The AMS distributes Séminares et Congrès in the United States, Canada, and Mexico. Orders from other countries should be sent to the Société Mathématique de France (SMF), Maison de la SMF, case 916-Luminy-F-13288 Marseille cedex 09, France, or to Institut Henri Poincaré, 11 rue Pierre et Marie Curie, 75231 Paris cedex 05, France. Individual AMS member price is listed. Members of SMF in North America receive a 30% discount from list price. Softcover.