Frati, Fabrizio, Michael Kaufmann, János Pach, Csaba Tóth, and David Wood. “On the Upward Planarity of Mixed Plane Graphs”. Journal of Graph Algorithms and Applications 18, no. 2 (May 1, 2014): 253–279. Accessed December 27, 2024. https://jgaa.info/index.php/jgaa/article/view/paper322.