Columbia subject headings:
Harvard subject headings:
Catholic Church--Doctrines.
Catholic Church--Oriental rites.
Catholic Church--Relations--Eastern churches.
Eastern churches--Doctrines.
Eastern churches--Relations--Catholic Church
Papacy and Christian union.
Schism--Eastern and Western Church.
Schism.
Princeton subject headings:
Catholic Church--Relations--Eastern churches.
Eastern churches--Relations--Catholic Church.