Atkinson, M. D., S. A. Linton, and L. A. Walker. “Priority Queues and Multisets”. The Electronic Journal of Combinatorics 2, no. 1 (November 10, 1995): R24. Accessed March 14, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v2i1r24.