Berta, T., Árki, Z.:
Why it is so hard to choose a good open problem for cooperative work in primary mathematics education?.
In: ICERI2021 Proceedings : 14th annual International Conference of Education, Research and Innovation. Ed.: by Luis Gómez Chova, Agustín López Martínez, Ignacio Candel Torres, IATED Academy, Valencia, 6576-6580, 2021, (ISSN 2340-1095) ISBN: 9788409345496