Columbia subject headings:
Bulgaria--History--1762-1878.
Obretenov, Nikola T. (Nikola Tikhov), 1849-1939.
Revolutionaries--Bulgaria--Biography.
Harvard subject headings:
Bulgaria--History--1762-1878.
Obretenov, Nikola T. (Nikola Tikhov), 1849-1939.
Revolutionaries--Bulgaria--Biography
Princeton subject headings:
Bulgaria--History--1762-1878.
Bulgaria--History--1878-1944.
Obretenov, Nikola T. (Nikola Tikhov), 1849-1939.
Revolutionaries--Bulgaria--Biography.