Aboulker, Pierre, Frédéric Havet, Kolja Knauer, and Clément Rambaud. “On the Dichromatic Number of Surfaces”. The Electronic Journal of Combinatorics 29, no. 1 (February 11, 2022): #P1.30. Accessed May 28, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v29i1p30.