https://www.inopressa.ru/article/26Nov2018/dailybeast/spy.html
http://www.rosbalt.ru/business/2018/11/26/1748828.html
“Natural causes” can’t be ruled out. But those include stress, and there’s no doubt Gen. Korobov of the G(R)U was under a lot of that.
https://www.thedailybeast.com/inside-the-mystery-of-the-dead-russian-spy-chief
https://www.inopressa.ru/article/23Nov2018/handelsblatt/kaspersky.html
http://www.ng.ru/economics/2018-11-23/5_7446_nedra.html
http://www.dsnews.ua/world/smert-nachalnika-gru-kak-putin-naryadilsya-v-nikolaya-i-22112018220000
https://www.depo.ua/ukr/svit/kinec-korobova-chomu-tak-chasto-ginut-putinski-shpiguni-20181122873929
https://www.rbc.ru/newspaper/2018/11/22/5bf41d339a79473deff871b2
https://www.kommersant.ru/doc/3806539