Nisonger, Thomas E.
Libraries Unlimited, 1992
Buku Referensi
Stouthamer-Loeber, Magda
Sage, 1995
Buku Teks
Harris, Lesley Ellen
American Management Association, 2009
eBooks
Lee, Stuart D.
Facet Publishing, 2004
Buku Teks
Loertscher, David V.
Hi Willow Research & Publishing, 2009
Buku Referensi