Bianchi, Stefano, Christian Mastrodonato, Gianni Vercelli, and Giuliano Vivanet. “Use of Ontologies to Annotate and Retrieve Educational Contents: The AquaRing Approach”. Journal of e-Learning and Knowledge Society 5, no. 1 (November 16, 2009). Accessed October 28, 2021. https://www.je-lks.org/ojs/index.php/Je-LKS_EN/article/view/308.