Lewis, Norman
Harper & Row , 1962
Buku Referensi
Shurter, Robert L.
McGraw-Hill, 1959
Buku Teks SO
editor, Bud Wileman, Robin Wileman, Bessana C. Sewell
Wileman Publications, 1986
Buku Referensi
Uta Frith edited
Academic Press, 1980
Buku Teks SO
Cutts, Martin
Oxford University Press, 1995
Buku Teks