Regesta Imperii Akademie der Wissenschaften This link opens in a new windowThe RI OPAC is a freely accessible literature database for medieval research in the entire European language area, covering all disciplines. The database serves both the regestae database as source for the cited literature, as well as universal research tool for searching for publications. Specialist literature from the 16th century onwards is taken into account, which deals with the period from Late Antiquity to the Reformation.