1. Department of Mathematics, Faculty of Science and Information Technology, Irbid National University, Irbid 21110, Jordan
2. Department of Mathematics and Computer Sciences, “Dunǎrea de Jos” University of Galati, 111, Domneascǎ Street, 800201 Galati, Romania
3. Department of Mathematics, Université de Caen Basse-Normandie, F-14032 Caen, France
4. Department of Mathematical Sciences, United Arab Emirates University, Abu Dhabi P.O. Box 15551, United Arab Emirates