https://www.kommersant.ru/doc/3842396
http://www.kasparov.ru/material.php?id=5C22704D734B3
https://www.gazeta.ru/army/2018/12/25/12108535.shtml
https://www.kommersant.ru/doc/3842391
Regional experts also predicted that Russia may look to take advantage of the uncertainty created by James Mattis's resignation as President Trump's defense secretary.
https://www.newsweek.com/ukraine-russia-war-attack-christmas-1270621
https://www.gazeta.ru/politics/2018/12/24_a_12106099.shtml
https://www.gazeta.ru/politics/2018/12/24_a_12106207.shtml
https://www.kommersant.ru/doc/3841521
http://www.kasparov.ru/material.php?id=5C20BC4282C5D