Chruden, Herbert J.
South-Western, 1966
Buku Teks
Jenks, James M.
New Jersey : Alexander Hamilton Institute, Inc,
Buku Referensi
Chruden, Herbert J.
South-Western Publishing Co., 1976
Buku Teks
Chruden, Herbert J.
South-Western , 1966
Buku Teks
Goyal, R.C., author
Prenctice Hall of India, 1998
Buku Teks