Ding, Guoli, Joshua Fallon, and Emily Marshall. “On Almost-Planar Graphs”. The Electronic Journal of Combinatorics 25, no. 1 (March 16, 2018): P1.55. Accessed March 16, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v25i1p55.