John Wiley & Sons, 2003
Buku Teks
edited by Karen Harrison and Bernadette Rainey
Wiley-Blackwell, 2013
Buku Teks
Merriam-Webster's, Incorporated, 1993
Buku Referensi
Burke, Michelle Marie, Author
American Management Association, 1997
eBooks
Merriam-Webster, 2000
Buku Referensi