It's one of the 4 canonic Dzogchen cycles in Yungdrung Bön.
These 4 and their respective commentaries / instruction manuals are:
Zhang Zhung Nyen Gyü & Gyalwa Chaktri
Drakpa Korsum & Yangtse Longchen
Gabpa Gukor & A Tri
Yetri Tasel & Namkha Trüldzö
"Drakpa Korsum" means "The Triple Proclamation", referring to its transmission in 3 realms:
That of the Devas, Nagas & Humans.