Hamdi, Adel. “Symmetric Distribution of Crossings and Nestings in Permutations of Type $B$”. The Electronic Journal of Combinatorics 18, no. 1 (October 10, 2011): #P200. Accessed May 2, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v18i1p200.