Goldstein, Elisha, author
Atria Books, 2012
Buku Teks
Engel, Baverly, author
John Wiley & Sons, 2004
Buku Teks
Weiss, Marisa C., author
Times Books , 1998
Buku Teks
Kemp, Jana, author
American Management Association, 2005
eBooks
Tracy, Brian, author
John Wiley & Sons, 2003
Buku Teks