Columbia subject headings:
Bulgaria--Foreign relations--Catholic Church.
Catholic Church--Bulgaria--History--20th century.
Catholic Church--Foreign relations--Bulgaria.
John XXIII, Pope, 1881-1963.
Harvard subject headings:
Bulgaria--Church history--20th century.
Bulgaria--Foreign relations--Catholic Church.
Catholic Church--Bulgaria--History--20th century.
Catholic Church--Foreign relations--Bulgaria.
John XXIII, Pope, 1881-1963.
Princeton subject headings: