Columbia subject headings:
Harvard subject headings:
Bunkers (Fortification)--Greece--History--20th century.
Fortification--Greece--History--20th century.
Metaxas-Line (Greece)--History--20th century.
Military art and science--Greece--History--20th century.
Princeton subject headings:
Fortification--Greece--History--20th century.
Greece--History, Military.
Greece--History--Occupation, 1941-1944.