Columbia subject headings:
Communists--Bulgaria--Biography.
Political prisoners--Soviet Union--Biography.
Popov, Blagoĭ, 1902-
Harvard subject headings:
Princeton subject headings:
Bulgaria--Politics and government--1878-1944.
Political prisoners--Bulgaria--Biography.
Political prisoners--Russia (Federation)--Siberia--Biography.
Popov, Blagoĭ, 1902-
Siberia (Russia)--History--1917-