作者: William T Trotter , John I Moore
DOI: 10.1016/0095-8956(77)90048-X
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摘要: Abstract A partially ordered set (poset) is planar if it has a Hasse diagram. The dimension of bounded poset at most two. We show that the having greatest lower bound three. also construct four-dimensional posets, but no with larger than four known. called tree its diagram in graph-theoretic sense. three and give forbidden subposet characterization two-dimensional trees.