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

https://ecipe.org/wp-content/uploads/2021/09/ECI_21_PolicyBrief_13_2021_LY02.pdf

https://www.bruegel.org/2022/02/preparing-for-the-first-winter-without-russian-gas/