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Proving a witness lemma in better-quasiordering theory: the method of ‘extensions’

Published online by Cambridge University Press:  28 June 2011

Igor Kříž
Igor Kříž
Affiliation:
The Ohio State University, Department of Mathematics, Columbus, Ohio 43210, U.S.A.
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Abstract

We introduce a new method for proving ‘witness lemmas’ in BQO theory. As an application, we obtain witness-lemmas for arbitrary trees and for σ-scattered linear orderings. A positive answer to a question by Van Engelen, Miller and Steel follows.

Type
Research Article
Information
Mathematical Proceedings of the Cambridge Philosophical Society , Volume 106 , Issue 2 , September 1989 , pp. 253 - 262
Copyright
Copyright © Cambridge Philosophical Society 1989

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