1. Department of Electrical and Computer Engineering, University of Western Macedonia, 50131 Kozani, Greece
2. Faculty of Medicine and Dentistry (Malta Campus), Queen Mary University of London, VCT 2520 Victoria, Malta
3. Human Computer Interaction Laboratory (HCILab), Department of Informatics and Telecommunications, School of Informatics and Telecommunications, University of Ioannina, 47100 Arta, Greece