The edge-density of 4-critical planar graphs

Abstract

Improving a recent result of G. Koester, it is shown that there exist 4-critical planar graphs in which the number of edges is more than twice the number of vertices.

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References

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Grünbaum, B. The edge-density of 4-critical planar graphs. Combinatorica 8, 137–139 (1988). https://doi.org/10.1007/BF02122562

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AMS subject classification (1980)

  • 05 C1 5