Dowling, Barbara Tolley
Newbury House Publishers , 1982
Buku Teks
Lesikar, Raymond V. (Raymond Vincent), author
McGraw-Hill/Irwin , 2002
Buku Teks
Hanks, Patrick
Cambridge University Press, 1990
Buku Teks
Voiles, Price R.
Glencoe, 1993
Buku Teks
Guffey, Mary Ellen, author
Cengage Learning Asia, 2008
Buku Teks