Artikel Jurnal
Ellis, Estelle, author
Thames and Hudson, 1998
Buku Referensi
Rashelle S. Karp, editor
[American Library association, American Library association], 2002
eBooks
Alexander, Roy, 1925- , author
American Management Association;, 2009
eBooks
Mogadam, Michael, author
New American Library, 2001
Buku Teks