Vietnamese religious material comes in two layers that were written for different audiences in different scripts, and both matter.
The classical layer is in literary Chinese. The Viet Dien U Linh Tap and the Linh Nam Chich Quai, from the fourteenth and fifteenth centuries, collect accounts of the country's spirits and legendary history, and they were compiled by scholar-officials working within a Confucian literary tradition and in part to establish which deities the state should recognise. Alongside them sit the imperial recognitions themselves, issued to villages for their tutelary gods, which survive in large numbers and constitute an administrative record of the pantheon.
The popular layer is largely oral and performed. The chau van songs of the hau dong, the ritual in which mediums host the spirits of the four palaces in sequence, carry the characterisation of each figure, and the ritual is the primary place where the pantheon is actually enacted rather than described.
Twentieth-century politics interrupted the record. Mediumship was discouraged and at times suppressed as superstition, and open practice contracted. Since the late 1980s it has revived vigorously and visibly, and in 2016 the practices connected with the Mother Goddesses were inscribed on an international heritage list, which has brought recognition, funding, tourism and new arguments about authenticity all at once.