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

https://www.aei.org/wp-content/uploads/2020/02/Countering-America%E2%80%99s-Regional-Economic-Disparities-Is-Going-to-Take-More-Than-Hope.pdf

http://www.kas.de/wf/doc/kas_450-2190-2-30.pdf?170424105349