Crystal, David, 1941-, author
Westview Press, 1980
Buku Referensi
edited by Ruslan Mitkov
Oxford University Press, 2004
Buku Referensi
edited by John Lyons
Penguin Books, 1973
Buku Teks
Lehmann, Winfred P., author
Holt, Rinehart and Winston, 1962
Buku Teks
Gleason, H.A., author
Holt, Rinehart and Winston, 1955
Buku Teks