135
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JCT
2011
15 years 23 days ago
2011
Two non-isomorphic graphs are twins if each is isomorphic to a subgraph of the other. We prove that a rayless graph has either infinitely many twins or none.
147
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COMBINATORICA
2010
15 years 23 days ago
2010
We prove that every rayless graph has an unfriendly partition.