Fernandes, J. A., Ferreira Correia, P., & Roa Guzmán, R. (2010). ACQUISITION OF COMBINATORIAL OPERATIONS BY PRE-UNIVERSITY STUDENTS BY MEANS OF A TEACHING INTERVENTION. Revista Latinoamericana de Investigación en Matemática Educativa, 13(2), 215-242. https://relime.org/index.php/relime/article/view/319