AUTHOR=Zhang Yuting , Zhang Xiangwei , Lu Zhengnan , Zhu Dongdan TITLE=Structural characteristics and mechanism of collaborative environmental governance network of urban agglomerations: perspective of multilevel network JOURNAL=Frontiers in Environmental Science VOLUME=12 YEAR=2024 URL=https://www.frontiersin.org/journals/environmental-science/articles/10.3389/fenvs.2024.1478864 DOI=10.3389/fenvs.2024.1478864 ISSN=2296-665X