
https://www.crisisgroup.org/europe-central-asia/eastern-europe/ukraine/responding-new-crisis-ukraines-borders

http://www.css.ethz.ch/content/dam/ethz/special-interest/gess/cis/center-for-securities-studies/pdfs/ST2018.pdf

https://ukandeu.ac.uk/could-putin-be-tried-for-the-crime-of-aggression/?mc_cid=d756ca926a&mc_eid=815b1928ec