Marcel Das, Peter Ester, Lars Kaczmirek, editor
Routledge, 2011
Buku Teks
Agnew, Neil McK.
Prentice-Hall, 1982
Buku Teks
Sommer, Robert
New York, 2002
Buku Teks
Kimmel, Allan J.
Blackwell Publishing, 2007
Buku Teks
Kerlinger, Fred Nichols, 1910-
CBS College Publishing, 1986
Buku Teks