Dunn, Dana S., author
Longman, 2011
Buku Teks
Mahmoud, Shah, author
Betterway, 1992
Buku Referensi
Pechenik, Jan A., author
Pearson Longman, 2007
Buku Teks
Pechenik, Jan A., author
Longman , 2001
Buku Teks
O`Shea, Robert P. (Robert Paul), 1953-, author
Harcourt Brace & Company, 1996
Buku Teks