The overfull conjecture that a graph with maximum degree \Delta(G) \geq n/3 is class 2 if and only if it has an overfull subgraph S…
The overfull conjecture that a graph with maximum degree \Delta(G) \geq n/3 is class 2 if and only if it has an overfull subgraph S satisfying \Delta(S) = \Delta(G).
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Source: List of unsolved problems in mathematics (CC BY-SA 4.0)