Columbia subject headings:
Catholic Church--Relations--Orthodox Eastern Church.
Orthodox Eastern Church--Relations--Catholic Church.
Photius I, Saint, Patriarch of Constantinople, approximately 820-approximately 891.
Harvard subject headings:
Catholic Church--Relations--Orthodox Eastern Church.
Orthodox Eastern Church--Relations--Catholic Church.
Photius I, Saint, Patriarch of Constantinople, approximately 820-approximately 891.
Princeton subject headings:
Catholic Church--Relations--Orthodox Eastern Church.
Orthodox Eastern Church--Relations--Catholic Church.
Photius I, Saint, Patriarch of Constantinople, approximately 820-approximately 891.
Schism--Eastern and Western Church.