Columbia subject headings:
Bulgaria--Civilization.
Bulgaria--History--1393-1762.
Bulgaria--History--Sources.
Bulgaria--History--To 1393.
Harvard subject headings:
Bulgaria--Civilization.
Bulgaria--History--1393-1762.
Bulgaria--History--Sources.
Bulgaria--History--To 1393.
Princeton subject headings:
Bulgaria--Civilization.
Bulgaria--History--1393-1762.
Bulgaria--History--Sources.
Bulgaria--History--To 1393.