
https://sipri.org/media/press-release/2018/global-military-spending-remains-high-17-trillion

https://www.crisisgroup.org/europe-central-asia/eastern-europe/ukraine/261-peace-ukraine-iii-costs-war-donbas

https://www.friendsofeurope.org/wp/wp-content/uploads/2020/01/2020_FoE_SEC_PUB_Transatlantic_web.pdf