Sorokin, Pitirim A.
E. P. Dutton and Company, Inc., 1944
Buku Teks
Dean, Vera Micheles, author
Harvard University Press, 1948
Buku Teks
Likhachev, Dmitrii S.
Westview Press, 1991
Buku Teks
Granick, David
MIT Press, 1972
Buku Teks
edited by Klaus Gottstein
Westview Press, 1991
Buku Teks