Lendrum, Tony, author
McGraw-Hill, 1995
Buku Referensi
Bolland, Eric J., author
Emerald, 2017
eBooks
Matthews, Lawrence M., author
McGraw-Hill , 1983
Buku Teks
Minor, Marianne, author
PPM, 2005
Buku Teks
Dale, Margaret, author
Gramedia, 2003
Buku Teks