Barish, Robert D. “On the Number of $k$-Proper Connected Edge and Vertex Colorings of Graphs: Discrete and Computational Geometry, Graphs, and Games”. Thai Journal of Mathematics 21, no. 4 (December 31, 2023): 917–936. Accessed November 21, 2024. https://thaijmath2.in.cmu.ac.th/index.php/thaijmath/article/view/1556.