Firsan Nova, author
Rajawali, 2011
Buku Teks
Newsom, Doug, author
Wadsworth and Cengage Learning, 2013
Buku Teks
Cutlip, Scott M., author
Prentice-Hall, 1978
Buku Teks
Jefkins, Frank William, author
Butterworth-Heinemann , 1994
Buku Teks
Beard, Mike, author
Erlangga, 2001
Buku Teks