Lasher, William R.
Western College Publishing , 2000
Buku Teks
by Walter J. Wadsworth
Gemini Books, 2000
Buku Referensi
Budd, Thomas A.
Alexander Hamilton Institute, 1961
Buku Teks
Allen, David
Crest Publishing House, 2002
Buku Teks
by Joseph T. Straub
Gemini Books, 2000
Buku Referensi