Collier McMillan , 1964
Buku Teks
London Collier-Macmillan 1965,
Buku Teks
Sambrook, G.A., author
Longmans, Green, 1947
Buku Teks
Parrot, Martin, author
Cambridge University Press, 2003
Buku Teks
Crystal, David, 1941-, author
Cambridge University Press , 2007
Buku Teks