Zeng, Qing, Yuefeng Yang, and Kaishun Wang. “$P$-Polynomial Weakly Distance-Regular Digraphs”. The Electronic Journal of Combinatorics 30, no. 3 (July 14, 2023): P3.3. Accessed March 29, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v30i3p3.