Six principal Nyingma monasteries

Six principal Nyingma monasteries;

Six "Mother" Nyingma Monasteries is a classical presentation of how, over the centuries, the nyingma have been upheld at six monastic seats:

1) Mindroling Monastery, in central Tibet, established in 1676, "upholds the Minling lineage".
2) Katok Monastery, in east Tibet, founded during the twelfth century, and expanded in 1656, is "the principal upholder of Rigdzin Düddul Dorje’s and Longsal Nyingpo’s lineages".
3)Dorje Drak Monastery, founded in central Tibet, in 1659, "upholds the Jangter or Northern Treasures lineage".
4) Palyul Monastery, founded in east Tibet in 1665, is "the principal upholder of Ratna Lingpa’s lineage and that of the Namchö, Sky Dharmas.
5) Dzogchen Monastery, in east Tibet, established in 1685, is "the principal upholder of the Nyingtik".
6) Shechen Monastery founded in east Tibet, in 1735, "unifies the kama and terma lineages".