https://www.nytimes.com/2019/12/22/world/europe/bulgaria-russia-assassination-squad.html
https://glavcom.ua/economics/finances/gazove-peremirya-yaka-cina-kompromisu-648467.html
https://www.gazeta.ru/business/2019/12/22/12878240.shtml
http://www.ng.ru/economics/2019-12-22/1_7758_main.html
https://www.radiosvoboda.org/a/news-vitrenko-gazprom-tranzyt-ugoda/30337796.html