Columbia subject headings:
Bulgaria--History--1762-1878.
Bulgaria--History--1878-1944.
Bulgaria--History--1944-
Bulgaria--Politics and government.
Harvard subject headings:
Bulgaria--History--1762-1878.
Bulgaria--History--1878-1944.
Bulgaria--History--1944-
Bulgaria--Politics and government.
Princeton subject headings:
Bulgaria--History--1762-1878.
Bulgaria--History--1878-1944.
Bulgaria--History--1944-
Bulgaria--Politics and government.