Aichholzer, Oswin, Thomas Hackl, Sarah Lutteropp, Tamara Mchedlidze, Alexander Pilz, and Birgit Vogtenhuber. 2015. “Monotone Simultaneous Embeddings of Upward Planar Digraphs”. Journal of Graph Algorithms and Applications 19 (1):87-110. https://doi.org/10.7155/jgaa.00350.