Iwona Bak, Magdalena Ziolo, Katarzyna Cheba, Anna Spoz. Column Equation Solving Problems in Middle School Exam Paper. (CEMJP) [Internet]. 2015 Sep. 1 [cited 2024 Nov. 23];23(3):1-12. Available from: http://journals.kozminski.cem-j.org/index.php/pl_cemj/article/view/352