Stankova, Zvezdelina. “Shape-Wilf-Ordering on Permutations of Length 3”. The Electronic Journal of Combinatorics 14, no. 1 (August 20, 2007): R56. Accessed March 27, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v14i1r56.