Mohar, Bojan, and Petr Škoda. “Minimizing the Number of Label Transitions Around a Nonseparating Vertex of a Planar Graph”. Journal of Graph Algorithms and Applications 16, no. 2 (January 1, 2012): 225–241. Accessed June 17, 2025. https://jgaa-v4.cs.brown.edu/index.php/jgaa/article/view/paper256.