(1) Department of Mathematics, Notre Dame University, 46556 Notre Dame, IN, USA;(2) Abteilung Logik, Philosophisches Seminar der Universität Kiel, Olshausenstrasse, Haus 12a, D-2300 Kiel, Federal Republic of Germany
Abstract:
Supported by NSF Grant DMS 8601289 and a Humboldt Foundation Fellowship