1. School of Information Science and Technology, Yunnan Normal University, Yunnan, P. R. China
2. Department of Mathematics, Karnatak University, Dharwad 580003, India
3. Department of Mathematics, Davangere University, Shivagangothri, Davangere 577007, India
4. Fethiye Faculty of Business Administration, Mugla Sitki Kocman University, Mugla, Turkey
5. Department of Mathematics and Science Education, Harran University, Sanliurfa, Turkey