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

https://blogs.lse.ac.uk/europpblog/2023/03/13/what-impact-have-eu-sanctions-had-on-the-russian-economy/

http://www.guengl.eu/uploads/news-documents/Working_paper_Border_controls_on_cross_border_trade_in_goods.pdf