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A particularly interesting special case that is still open is: any digraph on n vertices with minimum outdegree at least n 3 contains a directed triangle. Short of proving this, one may seek a value(More)
It was conjectured by Caccetta and Häggkvist in 1978 that every digraph G with n vertices and minimum outdegree at least r contains a directed cycle of length at most dn=re. By refining an argument(More)