1. Department of Physics, School of Science, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece
2. S.M. Nikolskii Mathematical Institute, Peoples’ Friendship University of Russia (RUDN University), 117198 Moscow, Russia
3. Department of Physics, College of Science, Princess Nourah Bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia
4. Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense, Denmark