Columbia subject headings:
Europe--History, Military--20th century--Chronology.
Germany--History, Military--20th century--Chronology.
World War, 1914-1918--Causes.
World War, 1939-1945--Causes.
Harvard subject headings:
Europe--History--20th century--Chronology.
World War, 1914-1918--Causes--Chronology.
World War, 1914-1918--Chronology
World War, 1939-1945--Causes--Chronology.
World War, 1939-1945--Chronology.
Princeton subject headings: