Triplett, Kathy, author
Lark Books, 1997
Buku Referensi
Speight, Charlotte F., author
McGraw-Hill, 2004
Buku Teks
Leigh, Barbara
Djambatan, 1989
Buku Teks
editor by. Shahrudin Mohd Nor
ISI , 1996
Buku Referensi
Cosentino, Peter
Tiger Books International, 1993
Buku Teks