Pelto, Pertti J.
Harper & Row, Publishers, 1970
Buku Teks
Pelto, Pertti J.
Cambridge University press, 1978
Buku Teks
Jenks, Albert Ernest
American Association, 1937
Buku Teks
McGee, R. Jon
McGraw-Hill, 2012
Buku Referensi
Polity Press, 1999
Buku Teks