Crisp, Richard D., author
McGraw-Hill, 1957
Buku Teks
Aaker, David A., author
John Wiley & Sons, 2000
Buku Teks
Kress, George
Prentice-Hall, 1988
Buku Teks
Parasuraman, A., author
Addison-Wesley , 1991
Buku Teks
Breen, George Edward, 1911-, author
McGraw-Hill , 1982
Buku Teks