Columbia subject headings:
Bulgaria--History--Ferdinand I, 1887-1918--Sources.
Bulgaria--History--Interregnum, 1886-1887--Sources.
Bulgaria--Politics and government--1878-1944--Sources.
Ferdinand I, Czar of Bulgaria, 1861-1948--Sources.
Harvard subject headings:
Bulgaria--History--Ferdinand I, 1887-1918--Sources.
Bulgaria--History--Interregnum, 1886-1887--Sources.
Bulgaria--Politics and government--1878-1944--Sources.
Ferdinand I, Czar of Bulgaria, 1861-1948.
Princeton subject headings: