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Graph minors. IV: Tree-width and well-quasi-ordering. (English) Zbl 0719.05032
[Part III, cf. ibid. 36, 49-64 (1984; Zbl 0548.05025.]
The famous conjecture of K. Wagner says that if \(G_ 1,G_ 2,..\). is any countably infinite sequence of finite graphs, then there exist \(i,j,j>i\geq 1\) such that \(G_ i\) is isomorphic to a minor of \(G_ j\). By a result of Kruskal, this is true if all the \(G_ i's\) are trees. The authors extend Kruskal’s theorem to all sequences in which the first member \(G_ 1\) is planar. This is one of the steps towards establishing the truth of Wagner’s conjecture in general.

05C10 Planar graphs; geometric and topological aspects of graph theory
Full Text: DOI
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