Hoke, John Ray, editor
John Wiley & Sons, 2000
Buku Referensi
edited by Robert T. Packards
John Wiley & Sons, 1981
Buku Referensi
Cavers, David F
The University of Michigan Press, 1966
Buku Teks
Siegel, David D.
St.Paul Minn., 1982
Buku Teks
Leflar, Robert A.
The Michie Company, 1986
Buku Teks