Columbia subject headings:
World War, 1914-1918--Equipment and supplies.
World War, 1914-1918--Trench warfare.
Harvard subject headings:
World War, 1914-1918--Equipment and supplies
World War, 1914-1918--Trench warfare
Princeton subject headings:
World War, 1914-1918--Equipment and supplies.
World War, 1914-1918--Trench warfare.