Bouttier, J., and E. Guitter. “A Note on Irreducible Maps With Several Boundaries”. The Electronic Journal of Combinatorics 21, no. 1 (February 7, 2014): P1.23. Accessed March 17, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v21i1p23.