Z. Todorova - University of Chemical Technology and Metallurgy
N. Dishovsky - University of Chemical Technology and Metallurgy
R. Dimitrov - University of Chemical Technology and Metallurgy
Farid El-Tantawy - Suez Canal University
N. Abdel Aal
A. Al-Hajry - King Khalid University
M. Bououdina - King Khalid University