Ur, Penny, author
Cambridge University Press, 2006
Buku Teks
Ur, Penny, author
Cambridge University Press, 1991
Buku Teks
Ur, Penny, author
Cambridge University Press, 1999
Buku Teks
McArthur, Tom (Thomas Burns), author
Cambridge University Press, 1983
Buku Teks
Wetzell, A.D., author
McGraw-Hill, 1981
Buku Teks