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