1. Department for Continuing Education Research and Educational Technologies, University for Continuing Education Krems (Danube University Krems), 3500 Krems an der Donau, Austria
2. School of Educational Sciences, Tallinn University, 10120 Tallinn, Estonia
3. Centre for the Science of Learning & Technology (SLATE), Faculty of Psychology, University of Bergen, 5007 Bergen, Norway
4. Faculty of Information Technology and Communication Sciences, Tampere University, 33100 Tampere, Finland