Qualman, Erik, author
Wiley, 2009
Buku Teks
edited by William R. Miller, Kathleen M. Carroll
Guilford Press, 2006
Buku Teks
Allen, William Richard, 1924-, author
American Management Association, 1993
eBooks
The population council, 1999
Buku Teks
Staddon, John, author
McGraw-Hill, 2012
Buku Teks