Headington, Mark R.
Jones and Bartlett Publisher, 1997
Buku Teks
McCracken, Daniel D.
John Wiley & Sons, 1974
Buku Referensi
Schildt, Herbert
McGraw-Hill, 2001
Buku Teks
Pagan, Frank G.
John Wiley & Sons, 1976
Buku Teks
Conger, David
Pearson, 2002
Buku Teks