Author(s):
1. Dragana Milosavljević, University of Nis, Faculty of Sciences and Mathematics, , Serbia
2. Dragoljub Mirjanić, Akademija nauka i umjetnosti Republike Srpske, Republic of Srpska, Bosnia and Herzegovina
3. Darko Divnić, Akademija nauka i umjetnosti Republike Srpske, Republic of Srpska, Bosnia and Herzegovina
4. Tomislav Pavlović, University of Nis, Faculty of Sciences and Mathematics, , Serbia
5. Lana Pantić, University of Nis, Faculty of Sciences and Mathematics, , Serbia
6. Ivana Radonjić, University of Nis, Faculty of Sciences and Mathematics, , Serbia

Abstract