Siegel, David D.
St.Paul Minn., 1982
Buku Teks
Siegel, David D.
West Pub. Co., 1994
Buku Teks
Leflar, Robert A.
The Michie Company, 1986
Buku Teks
Cavers, David F
The University of Michigan Press, 1966
Buku Teks
Kay, Herma Hill, author
Harcourt Brace & Company, 1990
Buku Teks