Intelligent System Based on YOLOv9 for Emotion Detection in Educational Environments. SciELO Preprints, 2026. DOI: 10.1590/SciELOPreprints.17260. Disponível em: https://preprints.scielo.org/index.php/scielo/preprint/view/17260. Acesso em: 24 out. 2026.