The edge density of 4-critical planar graphs


Several constructions of 4-critical planar graphs are given. These provide answers to two questions of B. Grünbaum and give improved bounds for the maximum edge density of such graphs.

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Abbott, H.L., Zhou, B. The edge density of 4-critical planar graphs. Combinatorica 11, 185–189 (1991).

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AMS subject classification (1980)

  • Primary 05 C 15
  • Secondary 05 C 35