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• Current address, O.Guller:Ankara University, Faculty of Science, Department of Mathemat- ics, Ankara, Turkey. E-mail address : ozgeguller2604@gmail.com ORCID Address:
• Current address, E.Ibikli: Ankara University, Faculty of Science, Department of Mathematics, Ankara, Turkey. E-mail address : Ertan.Ibikli@ankara.edu.tr ORCID Address: http://orcid.org/0000-0002-4743-6229