House, C. Homer, author
Prentice-Hall, 1950
Buku Teks
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