1. NAAM Research Group, Department of Mathematics, Faculty of Science , King Abdulaziz University , P.O. Box 80203 , Jeddah , 21589 , Saudi Arabia
2. Department of Mathematics and Statistics, College of Art and Sciences , Khalifa University of Science and Technology , Abu Dhabi , United Arab Emirates
3. Al–Farabi Kazakh National University , Al–Farabi ave. 71, 050040 , Almaty , Kazakhstan
4. Institute of Mathematics and Mathematical Modeling , 125 Pushkin str., 050010 , Almaty , Kazakhstan
5. Department of Mathematics: Analysis , Logic and Discrete Mathematics Ghent University , Krijgslaan 281 , Ghent , Belgium