On planar and non-planar graphs having no chromatic zeros in the interval image Original Research Article

We exhibit a family of 2-connected graphs which is closed under certain operations, and show that each graph in the family has no chromatic zeros in the interval (1,2). The family contains not only collections of graphs having no certain minors, but also collections of plane graphs, including near-triangulations found by Birkhoff and Lewis [Chromatic polynomials, Trans. Amer. Math. Soc. 60 (1946) 355–451].