Columbia subject headings:
Harvard subject headings:
Denmark--Relations--Germany--Congresses.
Germany--Relations--Denmark--Congresses.
Schleswig (Germany and Denmark)--Archival resources--Congresses.
Princeton subject headings:
Archives--Denmark--History.
Archives--Germany--History.
Denmark--Relations--Germany.
Germany--Relations--Denmark.
Schleswig-Holsteinisches Landesarchiv.