1. Fraunhofer Institute for Applied Information Technology FIT, Germany
2. Department of Information Systems and New Media, University of Siegen, Germany
3. Fraunhofer Institute for Applied Information Technology FIT and Institute for Digital Consumption, University of Applied Science Bonn-Rhein-Sieg, Germany
4. Department of Information Systems and New Media, University of Siegen and Fraunhofer Institute for Applied Information Technology FIT, Germany