Duque, Frank, Hernán González-Aguilar, César Hernández-Vélez, Jesús Leaños, and Carolina Medina. “The Complexity of Computing the Cylindrical and the $t$-Circle Crossing Number of a Graph”. The Electronic Journal of Combinatorics 25, no. 2 (June 8, 2018): P2.43. Accessed March 27, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v25i2p43.