Brignall, Robert. “Labelled Well-Quasi-Order in Juxtapositions of Permutation Classes”. The Electronic Journal of Combinatorics 31, no. 2 (April 19, 2024): P2.21. Accessed March 15, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v31i2p21.