1. Center for Research and Development in Mathematics and Applications (CIDMA), Department of Mathematics; University of Aveiro; 3810-193 Aveiro Portugal
2. Faculty of Computer Science; Bialystok University of Technology; 15-351 Białystok Poland
3. Department of Mathematics; University of Trás-os-Montes e Alto Douro (UTAD); 5001-801 Vila Real Portugal
4. Institute of Systems and Robotics (ISR), Department of Electrical and Computer Engineering; University of Coimbra; 3030-290 Coimbra Portugal