Columbia subject headings:
Bulgaria--Foreign relations--1878-1944.
World War, 1914-1918--Bulgaria.
World War, 1914-1918--Diplomatic history.
Harvard subject headings:
Bulgaria--Foreign relations--1878-1944.
World War, 1914-1918--Bulgaria
World War, 1914-1918--Diplomatic history
Princeton subject headings:
Bulgaria--Foreign relations--1878-1944.
World War, 1914-1918--Bulgaria.
World War, 1914-1918--Diplomatic history.