Columbia subject headings:
Illustrated works.
Personal narratives.
Postcards--Germany--20th century.
World War, 1914-1918--Personal narratives, German.
World War, 1914-1918--Pictorial works.
Harvard subject headings:
Postcards--Germany--20th century.
World War, 1914-1918--Personal narratives, German
World War, 1914-1918--Pictorial works
Princeton subject headings:
Artists--Germany--20th century--Biography.
Catalogs.
Postcards--Germany--History--20th century.
Schubert, Otto, 1892-1970--Catalogs.
Schubert, Otto, 1892-1970.
World War, 1914-1918--Art and the war.