Author(s):
1. Jelena Penavin-Škundrić, Prirodno-matematički fakultet Banja Luka, Republic of Srpska, Bosnia and Herzegovina
2. Zora Levi, Republic of Srpska, Bosnia and Herzegovina
3. Slavica Sladojević, Republic of Srpska, Bosnia and Herzegovina
4. Rada Petrovic, Republic of Srpska, Bosnia and Herzegovina
5. Darko Bodroža, Republic of Srpska, Bosnia and Herzegovina

Abstract