Feldman, Robert S., author
McGraw-Hill, 1985
Buku Teks
Michael a. Hogg; Graham M. Vaughan
Prentice-Hall, 2002
Buku Teks
Lapiere, R.T.
McGraw-Hill , 1942
Buku Teks
Michener, Andrew, author
Thomson, 2004
Buku Teks
Baron, Robert A., author
Allyn and Bacon , 1997
Buku Teks