1. Doctoral Programme in Education and ICT (e-Learning), Research Line Challenges for Sustainable Management and Organization in Online Education, Universitat Oberta de Catalunya, 08018 Barcelona, Spain
2. Faculty of Information Engineering, Computer Science and Statistics, Sapienza University of Rome, 00185 Rome, Italy
3. Faculty of Economic and Business, Universitat Oberta de Catalunya, 08018 Barcelona, Spain
4. Department of Computer Control and Management Engineering, Sapienza University of Rome, 00185 Rome, Italy