Feng, Suling, Haoyue Wu, Guoxiang Li, Liping Li, and Wenting Zhou. “Convergence Analysis of Environmental Efficiency from the Perspective of Environmental Regulation: Evidence from China”. Technological and Economic Development of Economy 26, no. 5 (August 28, 2020): 1074-1097. Accessed July 2, 2024. https://aviation.vgtu.lt/index.php/TEDE/article/view/13233.