Planar graphs have two-coloring number at most 8
arXiv:1506.01412 · doi:10.1016/j.jctb.2017.12.003
Abstract
We prove that the two-colouring number of any planar graph is at most 8. This resolves a question of Kierstead et al. [SIAM J. Discrete Math.~23 (2009), 1548--1560]. The result is optimal.