Ashmore, Malcolm
Open University Press, 1990
Buku Teks
Illsley, Raymond
Nuffield provincial Hospitals Trust, 1980
Buku Teks
Weitz, Rose, author
Wadsworth and Cengage Learning, 2013
Buku Teks
Weis, Gregory L, author
Prentice Hall, 1996
Buku Teks
MacMillan Education Australia, 1995
Buku Teks