Columbia subject headings:
Mayer, Gustav, 1871-1948.
Harvard subject headings:
Jewish historians--Germany--Diaries.
Mayer, Gustav, 1871-1948--Correspondence.
Mayer, Gustav, 1871-1948.
Socialists--Germany--Correspondence.
World War, 1914-1918--Historiography
Princeton subject headings:
Historians--Germany--Biography.
Jews--Germany--Biography.
Mayer, Gustav, 1871-1948.
Socialists--Germany--Biography.