Eddelson, Michael, author
Oxford University Press, 1999
Buku Referensi
Murray Longmore [and others]
Oxford University press, 2014
Buku Teks
edited by Jeyanth Asheervath and Dorothy R. Blevins
Appleton-Century-Crofts, 1986.
Buku Referensi
Mortimore, Tilly, author
Whurr Publishers, 2006
Buku Teks
Lawrence, Norman; Watts, Joanna; Harrington, Richard; Hope, Sally
Oxford University Press, 1997
Buku Referensi