Wegmann, Brenda
Random House, 1985
Buku Teks SO
Cunningham, Sarah
Oxford University Press, 1994
Buku Teks SO
Cunningham, Sarah
Oxford University Press , 1994
Buku Teks SO
O`Connell, Daniel C.
Springer, 2012
eBooks
Wu, Hyong-sik
Language Plus, 2007
Buku Teks