Columbia subject headings:
Historians--Germany--Correspondence.
Ritter, Gerhard, 1888-1967--Correspondence.
Harvard subject headings:
Historians--Germany--Biography
Historians--Germany--Correspondence
Ritter, Gerhard, 1888-1967--Biography.
Ritter, Gerhard, 1888-1967--Correspondence.
Princeton subject headings:
Historians--Germany--Correspondence.
Ritter, Gerhard, 1888-1967.