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