Deegan, Heather, author
Routledge, 1996
Buku Teks
Lockman, Zachary, author
Cambridge, 2004
Buku Teks
Andersen, Roy R., author
Pearson/Prentice Hall, 2007
Buku Teks
Andersen, Roy R., author
Longman, 2012
Buku Teks
edited by David E. Long and Bernard Reich
Westview Press, 1986
Buku Teks