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COMBINATORICA
2006
14 years 9 months ago
2006
Given a universal binary countable homogeneous structure U and n , there is a partition of the induced n-element substructures of U into finitely many classes so that for any par...
COMBINATORICA
2006
14 years 9 months ago
2006
In this paper we show that, if G is a Berge graph such that neither G nor its complement G contains certain induced subgraphs, named proper wheels and long prisms, then either G i...
COMBINATORICA
2006
14 years 9 months ago
2006
We prove that the out-distance sequence {f+ (k)} of a vertex-transitive digraph of finite or infinite degree satisfies f+ (k + 1) f+ (k)2 for k 1, where f+ (k) denotes the numbe...
COMBINATORICA
2004
14 years 9 months ago
2004
We extend the basic theory concerning the cycle space of a finite graph to arbitrary infinite graphs, using as infinite cycles the homeomorphic images of the unit circle in the gr...
COMBINATORICA
2000
14 years 9 months ago
2000
Given a connected graph, X, we denote by 2 = 2(X) its smallest non-zero Laplacian eigenvalue. In this paper we show that among all sets of n - 1 transpositions which generate the ...