Document Type : Article
1 Department of Physics, Chemistry and Mathematics, Alabama A&M University, Normal, AL 35762-4900, USA.; Department of Mathematics and Statistics, Tshwane University of Technology, Pretoria-0008, South Africa.
2 Department of Mathematics, Faculty of Science and Arts, Yozgat Bozok University, 66100 Yozgat, Turkey
3 School of Electronics and Information Engineering, Wuhan Donghu University, Wuhan-430212, People's Republic of China
4 Department of Mathematics and Statistics, Tshwane University of Technology, Pretoria-0008, South Africa
5 Science Program, Texas A&M University at Qatar, P.O. Box 23874, Doha, Qatar