Tucker, Edwin W.
Irwin, 1992
Buku Teks
Guido, Ginny Wacker
Prentice-Hall, 2006
Buku Teks
Brooks, Elizabert C
Jones & Bartlett Learning, 2013
Buku Teks SO
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