Source: PL-Wn 12496 IV Graduale cistercienseFolio: 060rSequence: 15Feast: Cathedra PetriOffice: MASSGenre: ComCantus ID: g00262Mode: *Full text: Tu es Petrus*Notes: later addition; In Cathedra s. Petri RomaeMarginalia: RExternal image link: Image link