Whiteman, Natasha
Springer, 2012
eBooks
Hartley, R.J., author
Bowker-Saur, 1990
Buku Teks
Hammersley, Martyn, author
Paul Chapman Publishing, 2002
Buku Teks
Babbie, Earl R., author
Wadsworth, 2010
Buku Teks
edited by John I. Gallin and Frederick P. Ognibene
Academic press, 2007
Buku Teks