https://www.bbc.com/russian/news-46629251
http://www.ng.ru/cis/2018-12-20/5_7470_ukraine.html
http://www.dsnews.ua/politics/vizit-volkera-v-kiev-20122018220000
https://www.bbc.com/russian/news-46634112
https://www.novayagazeta.ru/articles/2018/12/20/78994-bolshe-konfrontatsii-bolshe-deneg
https://www.radiosvoboda.org/a/29663666.html
https://www.radiosvoboda.org/a/29663233.html