BUDÍNOVÁ, Irena; JANÍK, Tomáš. Children With Reduced Cognitive Efficiency and Addition of Natural Numbers up to 20: A Case Study. Journal of Elementary Education, [S. l.], v. 14, n. 2, p. 125–148, 2021. DOI: 10.18690/rei.14.2.125-148.2021. Disponível em: https://old.journals.um.si/index.php/education/article/view/1214. Acesso em: 8 nov. 2025.