Columbia subject headings:
Harvard subject headings:
France--Foreign relations--Germany--Ostfriesland--Sources--Catalogs.
Netherlands--Foreign relations--Germany--Ostfriesland--Sources--Catalogs.
Niedersächsisches STaatsarchiv in Aurich--Catalogs.
Ostfriesland (Germany)--Foreign relations--France--Sources--Catalogs.
Ostfriesland (Germany)--Foreign relations--Netherlands--Sources--Catalogs.
Princeton subject headings:
Ostfriesland (Germany)--History--Sources--Bibliography--Catalogs.