Philippines : De La Salle Univesrsity-Manila, 2005,
Majalah, Jurnal, Buletin
Bonner, Thomas Neville, author
Prentice-Hall, 1960
Buku Teks
edited by Jerrold R. Brandell
Free Press, 1997
Buku Teks
Williams, Malcolm, 1953-, author
Routledge, 2000
Buku Teks
Hickey, Joanne V., author
Philadelphia, 1996
Buku Teks