Herzog, Marcel, Gil Kaplan, Arieh Lev, and Romina Zigdon. “$r$-Critical Numbers of Natural Intervals”. The Electronic Journal of Combinatorics 28, no. 4 (December 3, 2021): P4.42. Accessed March 17, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v28i4p42.