1. Faculty of Mathematics and Computer Science, Babeş –Bolyai University, Cluj-Napoca, Romania
2. Department of Mathematics, Technical University of Cluj-Napoca, Cluj-Napoca, Romania
3. Faculty of Mathematics and Computer Science and Institute of Advanced Studies in Science and Technology, Babeş–Bolyai University, Cluj-Napoca, Romania
4. Tiberiu Popoviciu Institute of Numerical Analysis, Romanian Academy, Cluj-Napoca, Romania