Athenstädt, Jan Christoph, and Sabine Cornelsen. “Planarity of Overlapping Clusterings Including Unions of Two Partitions”. Journal of Graph Algorithms and Applications 21, no. 6 (October 1, 2017): 1057–1089. Accessed July 6, 2024. http://jgaa-v4.cs.brown.edu/index.php/jgaa/article/view/paper450.