Columbia subject headings:
Harvard subject headings:
Bulgaria--Foreign relations--United States.
United States--Foreign relations--1933-1945.
United States--Foreign relations--1945-1953.
United States--Foreign relations--Bulgaria.
World War, 1939-1945--Bulgaria.
Princeton subject headings:
Bulgaria--Foreign relations--United States.
United States--Foreign relations--1933-1945.
United States--Foreign relations--1945-1953.
United States--Foreign relations--Bulgaria.
World War, 1939-1945--Bulgaria.