Timms, Rita, author
Routledge, 1982
Buku Referensi
Gilbert, Neil, author
Allyn and Bacon, 1998
Buku Teks
Gilbert, Neil, author
Prentice-Hall, 1974
Buku Teks
Bell, Winifred, author
Macmillan, 1983
Buku Teks
Dobelstein, Andrew W., author
Wadsworth, 2003
Buku Teks