Eu, Sen-Peng, Tung-Shan Fu, Yu-Chang Liang, and Tsai-Lien Wong. “On $xD$-Generalizations of Stirling Numbers and Lah Numbers via Graphs and Rooks”. The Electronic Journal of Combinatorics 24, no. 2 (April 13, 2017): P2.9. Accessed March 17, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v24i2p9.