1. Adamič, M. (1996). Model sukcesivnega kombiniranja temeljnega in nivojskega pouka ter dosežki nivojskih skupin [Model of successive combination of basic and level education and achievements of level groups]. Sodobna Pedagogika [Modern Pedagogy], 47(1-2), 39-48.
2. Askew, M., & Wiliam, D. (1995). Recent research in mathematics education. HMSO/Osted.
3. Blanco Diez, J. C. (2018). Learning contexts available for Japanese teachers in a top tier public high school: Encompassing a demanding work environment with adult education needs. https://www.diva-portal.org/smash/get/diva2:1222725/FULLTEXT01.pdf
4. Boaler, J. (1997). Setting, social class and survival of the quickest. British Educational Research Journal, 23(5), 575-596. https://doi.org/10.1080/0141192970230503
5. Burris, C. C., Heubert, J. P., & Levin, H. M. (2006). Accelerating mathematics achievement using heterogeneous grouping. American Educational Research Journal, 43(1), 137-154. https://doi.org/10.3102/00028312043001105