Lackie, J.M.
Elseiver Academic Press, 2007
Buku Referensi
Singleton, Paul
John Wiley & Sons, 1980
Buku Referensi
Alexander, Steve K.
McGraw-Hill, 2004
Buku Teks
edited by William Dodge Lewis, Henry Seidel Canby, Thomas Kite Brown
John C. Winston, 1942
Buku Referensi
R & R Newkirk/Longman, 1985
Buku Referensi