Summers, Edward Lee, author
Houghton Mifflin, 1989
Buku Teks
Bodnar, George H., author
Prentice Hall International, 1995
Buku Teks
Martin, Mearle, author
Prentice-Hall, 2003
Buku Teks
Gelinas, Ulric J., author
South-Western , 2005
Buku Teks
Page, John R., 1949-, author
Prentice-Hall, 1987
Buku Teks