From Rigpa Wiki
Ngor (Wyl. ngor) — one of the two main subschools of the Sakya tradition, founded by Ngorchen Kunga Zangpo (1382-1456). It is characterized by its rigorous discipline and knowledge of the tantras. It is famous for the so-called 'Seven mandalas of Ngor': Guhyasamaja, Hevajra, Chakrasamvara, Vajrayogini, Vajrabhairava, Sarvavidya and Mahakala.
- Ronald M. Davidson, 'The Ṅor-pa Tradition' in Wind Horse, Asian Humanities Press, 1981, pp. 79-98