Columbia subject headings:
Harvard subject headings:
Bulgaria--Foreign relations--Russia (Federation)
Bulgaria--History--1762-1878--Sources.
Bulgaria--History--1878-1944--Sources.
Bulgaria--History--Russo-Turkish War, 1877-1878--Sources.
Bulgaria--History--Uprising, 1876--Sources.
Bulgaria--Relations--Soviet Union--Sources.
Russia (Federation)--Foreign relations--Bulgaria.
Soviet Union--Relations--Bulgaria--Sources.
Princeton subject headings:
Bulgaria--History--1762-1878--Sources.
Bulgaria--History--Russo-Turkish War, 1877-1878--Sources.
Bulgaria--History--Uprising, 1876--Sources.
Eastern question (Balkan)