[1] Univ Tabriz, Fac Math Stat & Comp Sci, Tabriz, Iran
[2] Univ Tabriz, Res Dept Computat Algorithms & Math Models, Tabriz, Iran
[3] Univ Fribourg, Dept Math, CH-1700 Fribourg, Switzerland
[4] Martin Luther Univ Halle Wittenberg, Inst Math, Halle, Saale, Germany