Artikel Jurnal
Hirsch, Eric Donald, Jr., author
Sidney Schwartz, 1988
Buku Teks
Hirsch, Eric Donald, Jr., author
Schwartz Publishing, 1988
Buku Teks
Gaynor, Gerard H., author
American Management Association, 2004
eBooks
Tobias, Jeffrey
Bloomsbury , 1995
Buku Teks