Columbia subject headings:
Harvard subject headings:
Balkan Peninsula--Commerce.
Balkan Peninsula--Economic conditions.
Cities and towns--Balkan Peninsula.
Monasteries--Balkan Peninsula.
Princeton subject headings:
Balkan Peninsula--History--Congresses.
Byzantine Empire--History--Congresses.
Cities and towns, Medieval--Balkan Peninsula--Congresses.
Commerce--History--500-1500--Congresses.