1. Akay, M. (2018). The development of mathematics based STEM activities to be used in the education of gifted Students. [Unpublished master thesis]. Atatürk University, Erzurum, Turkey.
2. Akgündüz, D., Ertepınar, H., Ger, A. M., Kaplan Sayı, A., & Türk, Z. (2015). The report of STEM education workshop: An assessment on STEM education in Turkey. İstanbul Aydın University: STEM Center and Education Faculty. http://etkinlik.aydin.edu.tr/dosyalar/IAU_STEM_Egitimi_Calistay_Raporu_2015.pdf
3. Akkuş-Çıkla, O., & Duatepe-Paksu, A. (2006). Construction of a proportional reasoning test and its rubrics. Eurasian Journal of Educational Research, 25, 1-10.
4. Aladağ, A., & Dinç-Artut, P. (2012). Examination of students' problem-solving skills of proportional reasoning problems and realistic problems. İlköğretim Online, 11(4), 995-1010. https://www.ilkogretim-online.org/fulltext/218-1596968152.pdf?1635373281
5. Al-Wattban, M. S. (2001). Proportional reasoning and working memory capacity among Saudi adolescents: A neo-Piagetian investigation. [Unpublished PhD thesis]. University of Northern, Colorado.