Discrete Mathematics · 2004 · 51 citations · 6 references
Natural SciencesMathematicsCombinatoricsDirected Acyclic GraphsFundamental GroupGraph AlgorithmsGraph TheoryGroup TheoryAlgebraic Graph TheoryHamiltonian CyclesUnitary Operators
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George D. Birkhoff, Drew Lewis · Transactions of the American Mathematical Society · 1946 · 192 citations · Full text