http://www.radiosvoboda.org/content/article/27012355.html
http://www.worldaffairsjournal.org/article/putin-principle-how-it-came-rule-russia
http://russiancouncil.ru/inner/?id_4=5894&active_id_11=58
http://www.bbc.co.uk/russian/international/2015/05/150511_russian_military_ukraine_investigations
http://www.kommersant.ru/doc/2724484
http://r-studies.org/cms/index.php?action=news/view_details&news_id=3935&lang=ukr