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3.         Yetkiner Özel, Z. E., & Özel, S. (2013). Mathematics teacher quality: Its distribution and relationship with student achievement in Turkey. Asia Pacific Education Review, 14(2), 231-242. doi: 10.1007/s12564-013-9242-4

4.         Capraro, R. M., Capraro, M. M., Yetkiner, Z. E., Özel, S., Kim, H. G., & Küçük, A. R. (2010). An international comparison of Grade 6 students’ understanding of the equal sign. Psychological Reports, 106, 49-53.

5.         Erktin, E., Donmez, G., & Özel, S. (2006). Psychometric characteristics of the math anxiety scale. Education and Science, 31(140), 26-33.