Caeiro, M., J. Fontenla, and M. Llamas. “What Are My Students Doing? Introducing ELENA, the E-Learning Event Notification Architecture”. Cadernos De Informática, vol. 6, no. 1, May 2011, pp. 171-8, https://seer.ufrgs.br/index.php/cadernosdeinformatica/article/view/v6n1p171-178.