Columbia subject headings:
Bulgaria--History--1878-1944.
Bulgaria--Politics and government--1878-1944.
Kiril, Prince of Preslav, 1895-1945--Interviews.
Regents--Bulgaria--Interviews.
Harvard subject headings:
Bulgaria--History--1878-1944.
Bulgaria--Politics and government--1878-1944.
Regents--Bulgaria--Interviews.
Princeton subject headings:
Bulgaria--History--1878-1944.
Bulgaria--Politics and government--1878-1944.
Princes--Bulgaria--Biography.