Impedovo, Donato, Giuseppe Pirlo, and Erasmo Stasolla. “Integrated Virtual Environments for Collaborative Real-Time Activities: the Co.S.M.O.S. Prototype”. Journal of e-Learning and Knowledge Society 7, no. 2 (May 31, 2011). Accessed November 21, 2019. https://www.je-lks.org/ojs/index.php/Je-LKS_EN/article/view/521.