Parker, R.H.
Penguin Books, 1972
Buku Teks
Fraser, Lyn M., author
Prentice-Hall International, 1995
Buku Teks
Foster, Louis O., author
Chelton, 1961
Buku Teks
by Joseph T. Straub
Gemini Books, 2000
Buku Referensi
Budd, Thomas A., author
Alexander Hamilton Institute, 1961
Buku Teks