YU, Guanqi. Analysis of changes and trends in ambient air pollutant concentrations in the Beijing-Tianjin-Hebei region in recent years. Highlights in Science, Engineering and Technology, [S. l.], v. 11, p. 201–209, 2022. DOI: 10.54097/hset.v11i.1376. Disponível em: https://drpress.org/ojs/index.php/HSET/article/view/1376. Acesso em: 25 may. 2026.