Curtis, Michael, author
Harper & Row, 1978
Buku Teks
Lipson, Leslie, author
Prentice-Hall, 1965
Buku Teks
Ethridge, Marcus E., author
Wadsworth and Cengage Learning, 2013
Buku Teks
editors, Dermot Englefield, Gavin Drewry
Butterworth, 1984
Buku Referensi
edited by Avtar Brah and Annie E. Coombes
Routledge, 2000
Buku Teks