https://www.nato.int/nato_static_fl2014/assets/pdf/2021/6/pdf/210611-pr-2021-094-en.pdf
https://www.cesifo-group.de/DocDL/ifoDD_18-01_03-09_Ochsner.pdf
https://nationalinterest.org/feature/vladimir-putin-real-lessons-75th-anniversary-world-war-ii-162982
https://www.washingtonpost.com/graphics/2020/world/national-security/cia-crypto-encryption-machines-espionage/?utm_campaign=b064de4ef1-EMAIL_CAMPAIGN_2020_02_12_05_47&utm_medium=email&utm_source=POLITICO.EU