Cambridge University Press, 2009
eBooks
Bui, Yvonne N.
Sage , 2014
Buku Teks SO
Michael Nelson, Martha Craven Nussbaum, James V. Mirollo, Mera J. Flaumenhaft
Jossey-Bass, 2000
Buku Teks SO
edited by A. Grenfell Price
Angus & Robertson, 1959
Buku Teks SO
Kaufmann, Walter
Reader's Digest Press, 1977
Buku Teks SO