Besterfield, Dale H., author
Prentice-Hall, 1979
Buku Teks
by Howard S. Gitlow [and others]
McGraw-Hill, 2005
Buku Teks
Besterfield, Dale H., author
Pearson Education, 2004
Buku Teks
Banks, Jerry, author
John Wiley & Sons, c1989
Buku Teks
Fandy Tjiptono, author
Andi Offset, 1996
Buku Teks