Author/Authors :
Aghalary، Rasoul نويسنده Department of Mathematics, Faculty of Science, Urmia University, P.O. BOX 165, Urmia, Iran , , Ebadian، Ali نويسنده Department of Mathematics, Faculty of Science, Urmia University, P.O. BOX 165, Urmia, Iran , , Mafakheri، Mastore نويسنده Department of Mathematics, Faculty of Science, Urmia University ,