https://ecfr.eu/wp-content/uploads/Ambiguous-alliance-Neutrality-opt-outs-and-European-defence.pdf
http://HTTPS://WWW.WHITEHOUSE.GOV/WP-CONTENT/UPLOADS/2017/12/NSS-FINAL-12-18-2017-0905-2.PDF
https://www.brookings.edu/articles/the-russia-ukraine-war-and-its-ramifications-for-russia/?utm_campaign=Brookings%20Brief&utm_medium=email&utm_content=237480315&utm_source=hs_email
https://www.iai.it/sites/default/files/iaip1924.pdf