Anthony, Michael
Houghton Mifflin, 1967
Buku Teks
Scott, Gini Graham, author
American Management Association, 2007
eBooks
Welles, Chris
E.P. Dutton & Co., 1975
Buku Teks
Mahar, Paul
Sams.net, 1997
Multimedia
Shakespeare, William, 1564-1616, author
Penguin Books, 1970
Buku Teks