1. Mathematical Institute, Slovak Academy of Sciences, Bratislava, Slovakia
2. Institute for Research and Applications of Fuzzy Modeling, University of Ostrava, Ostrava, Czech Republic
3. Department of Mathematics and Descriptive Geometry, Faculty of Civil Engineering, Slovak University of Technology Bratislava, Bratislava, Slovakia
4. School of Mathematics Science, Suzhou University of Science and Technology, Suzhou, Jiangsu, People's Republic of China
5. School of Mathematics and Statistics, Yancheng Teachers University, Jiangsu, People's Republic of China