Buku Referensi
Leech, Geoffrey N., 1936-, author
Edinburgh University Press, 2006
Buku Referensi
Phythian, B.A.
Hodder & Stoughton, 1980
Buku Teks
Parrot, Martin, author
Cambridge University Press, 2003
Buku Teks
Jepson, R. W.
Longman , 1936
Buku Teks