Columbia subject headings:
Bulgaria--History.
Europe--Politics and government--1871-1918.
Great Britain--Foreign relations--Soviet Union.
Soviet Union--Foreign relations--Great Britain.
Soviet Union--History--Revolution, 1917-1921.
Harvard subject headings:
Bulgaria--History.
Europe--Politics and government--1871-1918.
Great Britain--Foreign relations--Soviet Union.
Soviet Union--Foreign relations--Great Britain.
Soviet Union--History--Revolution, 1917-1921.
Princeton subject headings:
Bulgaria--History.
Europe--Politics and government--1871-1918.
Great Britain--Foreign relations--Soviet Union.
Soviet Union--Foreign relations--Great Britain.
Soviet Union--History--Revolution, 1917-1921.