Columbia subject headings:
Harvard subject headings:
Police--Russia--History--19th century.
Police--Soviet Union.
Revolutionaries--Soviet Union
Russia--History--Nicholas I, 1825-1855.
Russia--Politics and government--1825-1855.
Russia--Politics and government--1855-1881.
Secret service--Russia--History--19th century.
Princeton subject headings:
Police--Russia--History.
Secret service--Russia--History.