Aguru and related terms appear in later Sanskrit, Chinese and Arabic sources, but which candidate early mention, several sit in texts of disputed date, is genuinely the earliest surviving reference has not been settled against a securely dated source.
What would resolve this A philological study fixing the earliest secure and datable occurrence of aguru or a cognate term in a text whose date scholars agree on, or an archaeobotanical identification of Aquilaria resin residue from a securely dated find.
OpenPhilology, archaeobotanyMircea Eliade (ed.); Lindsay Jones (ed., 2nd ed.), Encyclopedia of Religion