Dollhopf J, Goulden I, Greene C. Words Avoiding a Reflexive Acyclic Relation. Electron. J. Combin. [Internet]. 2006Feb.8 [cited 2026Jul.8];11(2):#R28. Available from: https://www.combinatorics.org/ojs/index.php/eljc/article/view/v11i2r28