1. Fraunhofer Institute for Applied Information Technology FIT, Sankt Augustin, Germany and Verbraucherinformatik Research Group, University of Siegen, Germany, Germany
2. Fraunhofer Institute for Applied Information Technology FIT, Sankt Augustin, Germany and Institut für Verbraucherinformatik, Bonn-Rhein Sieg University of Applied Science, Germany, Germany
3. Fraunhofer Institute for Applied Information Technology FIT, Sankt Augustin, Germany, Germany