University of MaraghehSahand Communications in Mathematical Analysis2322-580709120180101Density near zero33432368210.22130/scma.2018.23682ENElham BayatmaneshDepartment of Mathematics, Faculty of Basic Science, Shahed University, Tehran, Iran.Mohammad Akbari TootkaboniDepartment of Mathematics, Faculty of Basic Science, Shahed University, Tehran, Iran.20160924http://scma.maragheh.ac.ir/article_23682_545b6075235df500f5ed73aa31024524.pdf