1. Mediterranean University of Reggio Calabria, Department PAU, Via dell'Università 25 89124 Reggio Calabria, Italy
2. INdAM Unit, University of Catania, Italy
3. Institute of Mathematics for Industry, Kyushu University, Motooka, Nishi-ku, Fukuoka 819-0395, Japan
4. Graduate School of Mathematical Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8914, Japan
5. Honorary Member of Academy of Romanian Scientists, Ilfov, nr. 3, Bucuresti, Romania
6. Correspondence member of Accademia Peloritana dei Pericolanti, Piazza S. Pugliatti 1, 98122 Messina, Italy