Columbia subject headings:
Architecture, Medieval--Baltic States--Congresses.
Baltic States--Antiquities--Congresses.
Baltic States--History, Military--Congresses.
Castles--Baltic States--History--Congresses.
Harvard subject headings:
Architecture, Medieval--Baltic States--Congresses.
Baltic States--Antiquities--Congresses.
Baltic States--History, Military--Congresses.
Castles--Baltic States--History--Congresses.
Princeton subject headings: