Columbia subject headings:
Chaadaev, P. I︠A︡. (Petr I︠A︡kovlevich), 1794-1856--Correspondence.
Philosophy, Russian--History.
Philosophy.
Soviet Union--Intellectual life.
Harvard subject headings:
Chaadaev, P. I︠A︡. (Petr I︠A︡kovlevich), 1794-1856--Correspondence.
Philosophers--Soviet Union--Correspondence.
Philosophy.
Princeton subject headings:
History--Philosophy.
Philosophers--Soviet Union--Correspondence.
Philosophy.