Ulmer, Melville J., author
Houghton Miffiln, 1959
Buku Teks
Worthington, Ian, 1946-, author
Prentice-Hall, 2001
Buku Teks
edited by Rendings Fels
West Publishing, 1975
Buku Teks
Reder, Melvin Waren
Columbia University Press , 1947
Buku Teks
Lipsey, Richard G., 1928-, author
Harper Collin, 1996
Buku Teks