Wadsworth/Thomson Learning, 2004
Buku Teks
Denhardt, Robert B., author
Wadsworth and Cengage Learning, 2014
Buku Teks
Sage, 2018
Majalah, Jurnal, Buletin
Denhardt, Robert B., author
Harcourt College, 1999
Buku Teks
Gaus, John M., author
University of Alabama Press, 1055
Buku Teks