“Problems and difficulties in the process of teaching - learning in the subject of mathematics online modality of the pre-college in a university - Ecuador” (2020) Journal of Science and Research: Revista Ciencia e Investigación, 5(CININGEC), pp. 750–762. Available at: https://revistas.utb.edu.ec/index.php/sr/article/view/1036 (Accessed: 22 September 2026).