Columbia subject headings:
Europe--Foreign relations--Soviet Union.
Latvia--History--1914-1918.
Latvia--History--1918-1940.
Soviet Union--Foreign relations--Europe.
Harvard subject headings:
Europe--Foreign relations--Soviet Union.
Latvia--History--1914-1918.
Latvia--History--1918-1940.
Soviet Union--Foreign relations--Europe.
Princeton subject headings:
Europe--Foreign relations--Soviet Union.
Latvia--History--1914-1918.
Latvia--History--1918-1940.
Soviet Union--Foreign relations--Europe.