Griffith, Martin, author
Routledge, 2002
Buku Teks
edited by Beth A. Simmons and Richard H. Steinberg
Cambridge University Press, 2006
Buku Teks
Salvatore, Dominick, author
McGraw-Hill, 1975
Buku Teks
Spero, Joan Edelman, author
Wadsworth, 2010
Buku Teks
Maps Com, 2007
Buku Referensi