The existence of the underwater nuclear carrier, codenamed Kanyon by the U.S., has been rumoured in the past, but the leaked draft of Pentagon's Nuclear Posture Review confirmed this.
http://www.dailymail.co.uk/news/article-5270337/Russia-underwater-drone-carry-nuclear-bombs.html
https://day.kyiv.ua/ru/article/podrobnosti/gibridnaya-voyna-uzhe-na-more
http://www.rosbalt.ru/blogs/2018/01/15/1674500.html
https://www.rbc.ru/newspaper/2018/01/15/5a58ccd99a79475bf73470c1
https://www.rbc.ru/newspaper/2018/01/15/5a58d6449a7947629114e270
https://day.kyiv.ua/ru/blog/politika/volk-eshchyo-ne-na-psarne
http://www.kasparov.ru/material.php?id=5A5BBC70A965C
http://www.kasparov.ru/material.php?id=5A5B93613E82C
https://www.gazeta.ru/politics/2018/01/14_a_11612174.shtml