Columbia subject headings:
Strikes and lockouts--Coal mining--France--Nord (Department)
Strikes and lockouts--Coal mining--France--Pas-de-Calais.
World War, 1939-1945--Underground movements--France.
Harvard subject headings:
Strikes and lockouts--Coal mining--France--Nord (Department)
Strikes and lockouts--Coal mining--France--Pas-de-Calais.
World War, 1939-1945--Underground movements--France.
Princeton subject headings:
Strikes and lockouts--Coal mining--France--Nord (Dept.).
Strikes and lockouts--Coal mining--France--Pas-de-Calais.
World War, 1939-1945--Underground movements--France.