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On planar and non-planar graphs having no chromatic zeros in the interval(1,2). (English) Zbl 1148.05025
A chromatic zero of a graph $$G$$ is a zero of the chromatic polynomial of $$G$$. A near-triangulation is a loopless connected plane graph having at most one non-triangular face. The authors describe a family of 2-connected graphs closed under certain operations and having no chromatic zeros in $$(1,2)$$. The family contains collections of graphs avoiding certain minors and also collections of plane graphs, including near-triangulation found by G. Birkhoff and D. G. Lewis [Trans. Am. Math. Soc. 60, 355–451 (1946; Zbl 0060.41601)].
##### MSC:
 05C10 Planar graphs; geometric and topological aspects of graph theory 05C15 Coloring of graphs and hypergraphs
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##### References:
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