Columbia subject headings:
Bulgaria--History--1878-1944.
Bulgaria--History--1944-1990.
Bulgaria--Politics and government--1878-1944.
Bulgaria--Politics and government--1944-
Harvard subject headings:
Bulgaria--History--1944-1990.
Bulgaria--History--Boris III, 1918-1943.
Princeton subject headings:
Bulgaria--History--1944-1990.
Bulgaria--History--Boris III, 1918-1943.