Wright, Samson
Oxford University Press, 1931
Buku Referensi
Press, Frank
W.H. Freeman and Company, 1986
Buku Referensi
Weston, Paul B.
Prentoce-Hall, 1981
Buku Teks
Mott, Robert L.
Pearson Prentice Hall, 2006
Multimedia
edited by R.J. Johnston, Derek Gregory, Geraldine Pratt, Michael Watts
Blackwell Publishing, 2000
Buku Referensi