Columbia subject headings:
Belarus--Church history.
Catholic Church--Relations--Orthodox Eastern Church.
Orthodox Eastern Church--Relations--Catholic Church.
Poland--Church history.
Ukraine--Church history.
Union of Brest
Harvard subject headings:
Belarus--Church history.
Catholic Church--Relations--Orthodox Eastern Church.
Orthodox Eastern Church--Relations--Catholic Church.
Poland--Church history
Ukraine--Church history.
Union of Brest
Princeton subject headings: