Roskin, Michael G., 1939-, author
Pearson, 2017
Buku Teks
Academy of Political Science, 2018
Majalah, Jurnal, Buletin
Paul D. Stewart
D. Van Nostrand Company, INC, 1962
Buku Teks
Jacobsen, Gertude Ann
Barnes & Noble, 1951
Buku Teks
by Carlton Clymer Rodee [and others]
McGraw-Hill, 1983
Buku Teks