Martin, Ruben, author
Learning Matters, 2010
Buku Teks
Cohen, Nathan Edward, author
National Ass. of Workker, 1964
Buku Teks
Healy, Karen, author
Palgrave Macmillan, 2005
Buku Teks
Aspinwall-Roberts, Elaine, author
McGraw-Hill, 2012
Buku Teks
edited by Jerrold R. Brandell
Free Press, 1997
Buku Teks