Chen, William Y. C., and Sherry H. F. Yan. “Noncrossing Trees and Noncrossing Graphs”. The Electronic Journal of Combinatorics 13, no. 1 (August 14, 2006): #N12. Accessed April 12, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v13i1n12.