Khurmi, R. S.
Eurasia Publishing House, 1980
Buku Teks
Rees, Yvonne
Page One Publishing, 2001
Buku Referensi
Martin, James
Prentice-Hall, 1990
Buku Teks SO
Lazenby, Gina
Conran Octopus, 1999
Buku Referensi
Williamson, Hugh
Yale University Press, 1983
Buku Teks