Columbia subject headings:
Fortification--Poland--Modlin--History.
Modlin (Poland)--History, Military--19th century.
Twierdza Modlin--History.
Harvard subject headings:
Fortification--Poland--Modlin--History.
Fortification--Poland--Modlin.
Modlin (Poland)--History, Military--19th century.
Poland--History, Military--19th century.
Twierdza Modlin (Modlin, Poland)
Twierdza Modlin--History.
Princeton subject headings: