Columbia subject headings:
Harvard subject headings:
Fortification--Design and construction--History--17th century.
Fortification--Design and construction--History--18th century.
Fortification--History--17th century.
Fortification--History--18th century.
Princeton subject headings:
Fortification--Design and construction--History--17th century.
Fortification--Design and construction--History--18th century.
Fortification--History--17th century.
Fortification--History--18th century.