As a matter of fact, Zoroastrian priestly rituals constitute an interrelated network that is constructed according to varied degrees of complexity: the Visperad, Vendidad, and Nerangdin are ever more complex ritual elaboration of the Yasna. (...) To a certain degree, the Yasna is a structured arrangement, or compilation, of several units that, in different contexts and with certain modifications, are also performed as independent rituals.

- Michael Staussberg

( "Contextualizing the Contexts. On the study of Zoroastrian rituals", pp. 24-25 )