Malzahn, Nils, Sabrina Ziebarth, Dominik Kloke, and H. Ulrich Hoppe. “Self-Enriching Ontology-Based Casual Learning Games”. Computing and Informatics 34, no. 3 (October 24, 2015): 652–677. Accessed November 8, 2024. http://147.213.75.17/ojs/index.php/cai/article/view/3224.