Enis, Ben M., author
Goodyear, 1974
Buku Teks
Keller, kotler, author
Pearson Education, Inc, 2006
Buku Teks
Kotler, Philip, author
[publisher not identified], [date of publication not identified]
Buku Teks
Kotler, Philip, author
Prentice-Hall, 2000
Buku Teks
Wilson, Mike, author
Gower Publishing, 1985
Buku Teks