This division of the yanas is also found in Padmasambhava's "The Garland of Views"
(man ngag lta ba'i phreng ba) where the worldly views are further subdivided into:
- phyal ba (the unreflective)
- rgyang 'phen pa (Skt. Lokayata; the materialists)
- mur thug pa (Skt. Maryada; the nihilists)
- mu stegs pa (Skt. Tirthika; the extremists)
You can read more about it in the Dalai Lama's commentary on the man ngag lta ba'i phreng ba
*, or even more if you read "The Precious Vase".
you can also listen to the audio version of the Dalai Lama's commentary