Ferguson, Donald L., author
National Textbook, 1994
Buku Teks
C. Christhopher
Anmol Publicatioans PVT. Ltd, 1997
Buku Teks
Passante, Christopher K., author
Prenada Media Group, 2008
Buku Teks
Whale, John
Macmillan, 1972
Buku Teks
Ahuja, B. N., author
Surjeet Publications , 1992
Buku Teks