Sikich, Geary W.
McGraw-Hill, 1996
Buku Referensi
edited by Nancy Loudon
Churchill Livingstone, 1991
Buku Referensi
edited by John D. Edwards
Prentice-Hall, 1992
Buku Referensi
Palmer, Doc
McGraw-Hill, 1999
Buku Referensi
Everest, Suzanne
Bailliere Tindall , 1998
Buku Teks