Pritchard, Colin, author
Routledge, 2006
Buku Teks
edited by Bruce A. Thyer and John S. Wodarski
John Wiley, 2007
Buku Teks
Brown, Brian, author
Open University Press, 2003
Buku Teks
Jones & Bartlett Learning, 2018
Buku Teks
Ashford, Lori S., author
Population Reference Bureau, 2004
Buku Teks