Skaife, Linda
National Textbook Company, 1994
Buku Teks
Carpenter, Catrine, author
Gramedia Widiasarana Indonesia, 2000
Buku Teks
Bladon, Rachel
Passport Books, [date of publication not identified]
Buku Teks
Carpenter, Catrine, author
McGraw-Hill, 2004
Buku Teks
Neather, E.J.
MacMillan Press , 1985
Buku Teks