Randall, Geoffrey
Crest Publishing House, 2001
Buku Teks
Morse, Stephen A.
McGraw-Hill , 1967
Buku Teks
Kotler, Philip
[publisher not identified], [date of publication not identified]
Buku Teks
Kotler, Philip
Prentice-Hall, 2000
Buku Teks
Wilson, Mike
Gower Publishing, 1985
Buku Teks