Artikel Jurnal
Winston, Kwok Chee Chiu, author
pearson Prentice Hall, 2007
Buku Teks
Foulke, Roy Anderson, 1896-, author
McGraw-Hill, 1968
Buku Teks
Harrington, Diana R., 1940-, author
Toppan Company, 1991
Buku Teks
Rees, Bill
Prentice-Hall, 1990
Buku Teks