1. Department of Mathematics and Statistics, University of Victoria, Victoria, British Columbia V8W 3R4, Canada
2. Department of Medical Research, China Medical University Hospital, China Medical University, Taichung 40402, Taiwan
3. Department of Mathematics and Informatics, Azerbaijan University, 71 Jeyhun Hajibeyli Street, AZ1007 Baku, Azerbaijan
4. Section of Mathematics, International Telematic University Uninettuno, I-00186 Rome, Italy
5. Department of Mathematics, University of Swabi, Swabi 23561, Pakistan
6. Department of Pathogenic Microbiology & Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, 76 West Yanta Road, Xi’an 710061, People’s Republic of China
7. Department of Mathematics, College of Science & Arts, King Abdulaziz University, P.O. Box 344, Rabigh 21911, Saudi Arabia