Ore, Øystein (1962), Theory of graphs, American Mathematical Society Colloquium Publications, vol. 38, Providence, R.I.: American Mathematical Society, Theorem 13.1.5, p. 207, MR0150753
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Ore, Øystein (1962), Theory of graphs, American Mathematical Society Colloquium Publications, vol. 38, Providence, R.I.: American Mathematical Society, Theorem 13.1.5, p. 207, MR0150753