Bryson, John M., author
Jossey- Bass, 2011
Buku Teks
Latino, Robert J., author
CRC Press, 2011
Buku Teks
Rubin, Rhea Joyce, author
[American Library association, American Library association], 2006
eBooks
Nelson, Sandra, author
[American Management Association, ], 2009
eBooks
Ury, William, author
Bantam Books, 1992
Buku Teks