Seal, Bernard
Cambridge , 1999
Buku Referensi
Langan, John, 1942-
McGraw-Hill, 1992
Buku Teks
Spears, Deanne Milan
McGraw-Hill, 2000
Buku Teks
Haarman, Louann
Oxford University Press, 1989
Buku Teks
Grellet, Francoise
Cambridge University Press, 1994
Buku Referensi