Davis, Ralph Currier
Harper & Row, 1940
Buku Teks
William Wrenall, Quarterman Lee, editors in chief
McGraw-Hill, 1994
Buku Referensi
Yoder, Dale
Prentice-Hall, 1962
Buku Teks
Yoder, Dale
Prentice-Hall, 1984
Buku Teks
Bangs, John R.
Alexander Hamilton Institute, 1955; 1961
Buku Teks