Hardgrave, Robert L.
Harcourt, Brace, 1970
Buku Teks
edited by Stephan Haggard, Chung H. Lee and Sylvia Maxfield
Cornell University Press, 1993
Buku Teks
edited by Gabriel A. Almond, James S. Coleman
Princeton University Press, 1960
Buku Teks
Von der Mehden, Fred R.
Prentice-Hall, 1969
Buku Teks
Von der Mehden, Fred R.
Prentice-Hall, 1964
Buku Teks