Colouring normal quadrangulations of projective spaces

Tomáš Kaiser, On-Hei Solomon Lo, Atsuhiro Nakamoto +2

Youngs proved that every non-bipartite quadrangulation of the projective plane $\mathbb{R}{\mathrm{P}}^2$ is 4-chromatic. Kaiser and Stehl\'ık [J. Combin. Theory Ser. B 113 (2015),…