1. Department of Mathematics, Faculty of Science, Gazi University, Teknikokullar, 06500 Ankara, Turkey
2. Department of Mathematics, Faculty of Art and Science, Amasya University, Ipekkoy, 05100 Amasya, Turkey
3. Faculty of Education, Konya Necmettin Erbakan University, Meram, 42099 Konya, Turkey
4. Institute of Informatics, University of Gdańsk, Wita Stwosza 57, 80-952 Gdańsk, Poland