Author(s):
1. Stana Ristanović, Alumina doo, , Republic of Srpska, Bosnia and Herzegovina
2. Dragica Lazić, Republic of Srpska, Bosnia and Herzegovina
3. Dragana Kešelj, Republic of Srpska, Bosnia and Herzegovina
4. Dragana Blagojević, Prirodno-matematički fakultet Banja Luka, Republic of Srpska, Bosnia and Herzegovina
5. Slavica Sladojević, Republic of Srpska, Bosnia and Herzegovina
6. Gordana Ostojic, Republic of Srpska, Bosnia and Herzegovina