Petersen, Christian
Gower, 1994
Buku Teks SO
McDaniel, Carl
South Western Cengage Learning, 2013
Buku Teks SO
Armstrong, Gary M.
Prentice-Hall, 2005
Buku Teks SO
McDaniel, Carl
Salemba Empat , 2001
Buku Teks SO
Schoell, William F.
Allyn and Bacon, 1988
Buku Teks SO