Brooks, Elizabert C
Jones & Bartlett Learning, 2013
Buku Teks SO
Guido, Ginny Wacker
Prentice-Hall, 2006
Buku Teks SO
Tucker, Edwin W.
Richard D. Irwin, 1992
Buku Teks
Commons, John R.
University of Madison Press, 1959
Buku Teks SO
edited by, Diana M. Bailey, Sharan L. Schwartzberg
F.A. Davis , 1995
Buku Teks SO