Morgan, Thomas D.
ST. Paul MInn, 1978
Buku Teks
Fritscher, A. Lee
Little, Brown & Co., 1980
Buku Teks
Fisher, Bruce D, author
West Publishing Company, 1986
Buku Teks
Meiners, Roger E., author
Thomson/West , 2006
Buku Teks
Pegrum, Dudley F.
Richard D. Irwin, 1965
Buku Teks