Author/Authors :
Amiria, Z Department of Pure Mathematics - Ferdowsi University of Mashhad - Mashhad, Islamic Republic of Iran , Zarea, M Department of Pure Mathematics - Ferdowsi University of Mashhad - Mashhad, Islamic Republic of Iran , Kamyabi-Gola, R.A Department of Pure Mathematics - Ferdowsi University of Mashhad - Mashhad, Islamic Republic of Iran