University of Iowa, 2018
Majalah, Jurnal, Buletin
by Edwin Mansfield [and others]
Macmillan, 1971
Buku Teks
Burke, Karen C., 1951-, author
West Publishing, 1996
Buku Teks
Hamilton, Robert W., author
West Publishing, 1984
Buku Teks
Colombo, Ronald J., author
Oxford University Press, 2015
Buku Teks