Columbia subject headings:
Bulgaria--Church history--Middle Ages, 600-1500.
Orthodox Eastern Church--Relations--Catholic Church.
Photius I, Saint, Patriarch of Constantinople, approximately 820-approximately 891.
Harvard subject headings:
Bulgaria--Church history--Middle Ages, 600-1500.
Orthodox Eastern Church--Relations--Catholic Church.
Photius I, Saint, Patriarch of Constantinople, approximately 820-approximately 891.
Princeton subject headings:
Bulgaria--Church history--Middle Ages, 600-1500.
Catholic Church--Relations--Orthodox Eastern church.
Orthodox Eastern Church--Relations--Catholic Church.
Photius I, Saint, Patriarch of Constantinople, approximately 820-approximately 891.