
https://www.europarl.europa.eu/meetdocs/2009_2014/documents/deea/dv/2203_07/2203_07en.pdf

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

https://www.wto.org/english/news_e/pres18_e/pr820_e.htm