1. Thomas Johann Seebeck Department of Electronics, Tallinn University of Technology, Ehitajate tee 5, Tallinn, Estonia
2. Institut National des Sciences Appliquées de Rennes, 20 Avenue des Buttes de Coesmes, Rennes, France
3. Department of Cybernetics, Tallinn University of Technology, Ehitajate tee 5, Tallinn, Estonia