Columbia subject headings:
Commerce--History--Medieval, 500-1500.
Shipping--Mediterranean Region--History.
Harvard subject headings:
Contracts, Maritime--Mediterranean Region--History.
Mediterranean Region--Commerce--History.
Naval art and science--History
Naval battles--Mediterranean Sea--History.
Shipping--Mediterranean Region--History.
Princeton subject headings:
Commerce--History--Medieval, 500-1500.
Naval art and science--History.
Shipping--Mediterranean Region--History.