Jia, Chengye, and Weige Huang. “What Causes Differences in PM2.5 Concentration in China? Structures Are More Important”. The Economics and Finance Letters 9, no. 1 (March 11, 2022): 28–39. Accessed May 2, 2024. http://archive.conscientiabeam.com/index.php/29/article/view/2936.