
https://www.progressivepolicy.org/blogs/trade-fact-of-the-week-americas-non-mfn-tariffs-on-natural-resources-are-usually-low/

https://www.wto.org/english/res_e/reser_e/ullbergpresentation_e.pdf

http://www.chinadaily.com.cn/a/202005/06/WS5eb2013ba310a8b2411537e3.html