Columbia subject headings:
Bulgaria--History--Autonomy and independence movements.
Bulgaria--Relations--Russia (Federation)--History.
Bulgaria--Relations--Russia--History.
Bulgaria--Relations--Soviet Union--History.
Russia (Federation)--Relations--Bulgaria--History.
Russia--Relations--Bulgaria--History.
Soviet Union--Relations--Bulgaria--History.
Harvard subject headings:
Princeton subject headings:
Bulgaria--History--Autonomy and independence movements.
Bulgaria--Relations--Russia (Federation)--History.
Bulgaria--Relations--Russia--History.
Bulgaria--Relations--Soviet Union--History.
Russia (Federation)--Relations--Bulgaria--History.
Russia--Relations--Bulgaria--History.
Soviet Union--Relations--Bulgaria--History.