Seifter, Norbert, and Vladimir I. Trofimov. “Reachability Relations and the Structure of Transitive Digraphs”. The Electronic Journal of Combinatorics 16, no. 1 (February 27, 2009): #R26. Accessed May 1, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v16i1r26.