
https://www.politico.eu/article/shaky-grounds-secret-slipshod-evidence-eu-use-sanction-russia-oligarchs/

https://www.boeckler.de/pdf/p_wsi_report_52_2019.pdf

https://www.wilsoncenter.org/blog-post/helmut-kohl-collection-new-resource-post-cold-war-history