Almeida, Cesário, Luis Casas García, and Ricardo Luengo González. “Study of the Cognitive Structure of Portuguese Students in Years 9 (14-15 Year-Olds) and 12 (17-18 Year-Olds) Concerning the Notion of Probability: A Contribution of Theories of Nuclear Concepts and Threshold Concepts”. Revista Latinoamericana de Investigación en Matemática Educativa 20, no. 1 (March 31, 2017): 9–38. Accessed October 23, 2026. https://www.relime.org/index.php/relime/article/view/127.