Stimulating discussions with R. A. Pasmanter, as well as valuable comments from J. D. Opsteegh, F. Verhulst, and F. M. Selten, have helped in the investigation and preparation of this paper. Comments and criticisms by Michael Ghil and by three anonymous reviewers helped to improve the quality of the paper significantly. Financial support for this study came from the Netherlands Organization for Scientific Research (NWO).
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