Author(s):
1. Jelena Penavin-Škundrić, Prirodno-matematički fakultet Banja Luka, Republic of Srpska, Bosnia and Herzegovina
2. Zorica Levi, Faculty of Technology Banja Luka, Republic of Srpska, Bosnia and Herzegovina
3. Darko Bodroža, Republic of Srpska, Bosnia and Herzegovina
4. Milica Lolić, Faculty of Technology Banja Luka, Republic of Srpska, Bosnia and Herzegovina