1. Department of Mathematics, Ben-Gurion University of the Negev, Israel
2. DICEA—Università di Firenze via Santa Marta 3, Firenze 50139, Italy
3. DSMFI—Università di Parma, Parco Area delle Scienze 53/A, Parma 43134, Italy
4. Department of Mechanical Engineering, Ben-Gurion University of the Negev, Israel