Columbia subject headings:
Fortification--France--Saint-Omer (Pas-de-Calais)
Saint-Omer (Pas-de-Calais, France)--History.
Saint-Omer (Pas-de-Calais, France)--Pictorial works.
Harvard subject headings:
Princeton subject headings:
Fortification--France--Saint-Omer (Pas-de-Calais).
Saint-Omer (Pas-de-Calais, France)--History.
Saint-Omer (Pas-de-Calais, France)--Pictorial works.