Dourado, Mitre C., Fábio Protti, and Jayme L. Szwarcfiter. “Complexity Aspects of the Helly Property: Graphs and Hypergraphs”. The Electronic Journal of Combinatorics Dynamic Surveys (June 12, 2009): #DS17: Jun 2, 2009. Accessed April 12, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/DS17.