Bruhn, Henning, Laura Gellert, and Richard Lang. “Chromatic Index, Treewidth and Maximum Degree”. The Electronic Journal of Combinatorics 25, no. 2 (May 11, 2018): #P2.23. Accessed May 28, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v25i2p23.