منابع مشابه
Oriented trees in digraphs
Let f(k) be the smallest integer such that every f(k)-chromatic digraph contains every oriented tree of order k. Burr proved f(k) ≤ (k − 1)2 in general, and conjectured f(k) = 2k − 2. Burr also proved that every (8k − 9)-chromatic digraph contains every antidirected tree. We improve both of Burr’s bounds. We show that f(k) ≤ k2/2 − k/2 + 1 and that every antidirected tree of order k is containe...
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ژورنال
عنوان ژورنال: Discrete Mathematics
سال: 1991
ISSN: 0012-365X
DOI: 10.1016/0012-365x(91)90061-6