Columbia subject headings:
Boris III, Czar of Bulgaria, 1894-1943.
Bulgaria--History--Boris III, 1918-1943.
Bulgaria--Kings and rulers--Biography.
Harvard subject headings:
Boris III, Czar of Bulgaria, 1894-1943.
Bulgaria--History--Boris III, 1918-1943.
Bulgaria--Kings and rulers--Biography.
Princeton subject headings:
Boris III, Czar of Bulgaria, 1894-1943.
Bulgaria--History--Boris III, 1918-1943.
Bulgaria--Kings and rulers--Biography.