https://www.kommersant.ru/doc/4752183
https://www.ng.ru/world/2021-03-31/1_8116_italy.html
https://www.kommersant.ru/doc/4751215
https://ru.krymr.com/a/rossia-shpionazh-bolgaria/31173921.html
https://novayagazeta.ru/articles/2021/03/27/tochki-u-i-drugie-zveri
https://www.thetimes.co.uk/article/edinburgh-professor-gave-names-to-fake-russia-spy-68n2n3bzj
https://www.inopressa.ru/article/26Mar2021/wsj/bulgaria.html
https://www.wsj.com/articles/how-an-alleged-russianspyring-used-cold-war-tactics-11616701381