Gordon, Scott
Columbia University Press, 1980
Buku Teks
Midgley, James, author
Sage Publications, 1997
Buku Teks
Friedlander, Walter A., author
Prentice Hall of India, 1982
Buku Teks
Gilbert, Neil, author
Prentice-Hall, 1986
Buku Teks
Australian council of social service, 0
Buku Teks