Roskin, Michael G., author
Pearson/Prentice Hall, 2004
Buku Teks
MEI Publications Ltd, 2008
Majalah, Jurnal, Buletin
Rourke, John T., author
McGraw-Hill, 2007
Buku Teks
Ziegler, David M., author
Little, Brown, 1981
Buku Teks
Duchacek, Ivo D., author
Dryden Press, 1971
Buku Teks