ALTAMIRANO ÁLVAREZ, Martha Leonor. Manipulative materials to develop classification and seriation concepts in Early Childhood Education. Revista de Investigación Educativa Niveles, Ecuador, EC, v. 3, n. 2, p. 332–341, 2026. DOI: 10.61347/rien.v3i2.128. Disponível em: https://niveles.esprint.tech/index.php/niveles/article/view/128. Acesso em: 9 nov. 2026.