Artikel Jurnal
Graham, Michael Dennis, author
American Management Association, 2008
eBooks
Hongkong Kingsway International Publications 1981
Buku Referensi
Milkovich, George T., author
McGraw-Hill, Irwin, 2002
Buku Teks
Milkovich, George T., author
McGraw-Hill , 2008
Buku Teks