Schunk, Dale H.
Prentice-Hall, 1996
Buku Teks SO
edited by Stefan Engeser
Springer, 2012
eBooks
Smith, George Horsley
McGraw-Hill, 1954
Buku Teks SO
editors, Sandra L. Christenson, Amy L. Reschly, Cathy Wylie
Springer, 2012
eBooks
Cheskin, Louis
Liveright, 1959
Buku Teks SO