Porter, Rev
T. Nelson and Sons, Paternoster Row, 1891
Buku Teks
Orum, Anthony M.
Blackwell, 2003
Buku Teks
Kotler, Philip
Maxwell Macmillan International, 1993
Buku Teks
Kotler, Philip
John Wiley & Sons, Inc, 2000
Buku Teks
edited by Sara González
Routledge, 2018
Buku Teks