Defant, Colin, and James Propp. “Quantifying Noninvertibility in Discrete Dynamical Systems”. The Electronic Journal of Combinatorics 27, no. 3 (September 4, 2020): P3.51. Accessed March 29, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v27i3p51.