1. Department of Mathematics Education, Wonkwang University, Iksan, 570-749, Korea.
2. Serbian Academy of Sciences and Arts, 11000 Beograd, Serbia, and University of Niš, Faculty of Sciences and Mathematics, 18000 Niš, Serbia.
3. Division of Computing and Mathematics, University of Abertay, Dundee, UK.
4. Department of Mathematics, Vedant College of Engineering and Technology (Rajasthan Technical University), Bundi, 323021, Rajasthan, India.