1. Department of Mathematics, Università degli Studi di Bari “A. Moro”, Bari, Italy
2. Dipartimento di Matematica Tullio Levi-Civita, Università di Padova, Padova, Italy
3. Department of Mathematics, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague 2, Czechia
4. Laboratoire des signaux et systèmes, Université Paris-Saclay, CNRS, CentraleSupélec, Gif-sur-Yvette, France