Columbia subject headings:
Catholic Church--Relations--Orthodox Eastern Church.
Church history--Middle Ages, 600-1500.
Church history--Primitive and early church, ca. 30-600.
Orthodox Eastern Church--Relations--Catholic Church.
Patriarchs and patriarchate.
Harvard subject headings:
Catholic Church--Government--History--Research.
Patriarchs and patriarchate (Canon law)--Oriental Catholic churches.
Patriarchs and patriarchate (Catholic Oriental)
Patriarchs and patriarchate--History--Research.
Princeton subject headings:
Catholic Church--Government--History--Research.
Patriarchs and patriarchate (Canon law)--Oriental Catholic churches.
Patriarchs and patriarchate (Catholic Oriental)
Patriarchs and patriarchate--History--Research.