https://www.rosbalt.ru/blogs/2021/10/22/1927577.html
https://lansinginstitute.org/2021/10/12/russian-intelligence-focus-in-bulgaria/
https://www.rosbalt.ru/piter/2021/10/07/1925050.html
https://carnegie.ru/commentary/85479
https://jamestown.org/program/the-realities-of-russian-military-shipbuilding-part-one/