Columbia subject headings:
Belgium--History--German occupation, 1914-1918.
Industries--Belgium.
World War, 1914-1918--Economic aspects--Belgium.
Harvard subject headings:
Belgium--History--German occupation, 1914-1918.
Industries--Belgium
World War, 1914-1918--Economic aspects--Belgium.
Princeton subject headings:
Belgium--History--German occupation, 1914-1918.
Industries--Belgium.
World War, 1914-1918--Economic aspects--Belgium.