1. Department of Mathematics and Computer Sciences, Faculty of Natural Sciences, University of Gjirokastra, 6001 Gjirokastra, Albania
2. School of Computing, Union University, 11000 Belgrade, Serbia
3. Department of Mathematics, Faculty of Natural Sciences, University of Tirana, 1010 Tirana, Albania
4. Faculty of Electrical Engineering, University of Banja Luka, Patre 5, 78000 Banja Luka, Bosnia and Herzegovina
5. Faculty of Mechanical Engineering, University of Belgrade, Kraljice Marije 16, 11120 Beograd, Serbia