Hagopain, Mark N.
Longman, 1978
Buku Teks
Schippers, Birgit, author
Routledge, 2014
Buku Teks
edited by Robert E. Goodin, Charles Tilly
Oxford University Press, 2008
Buku Referensi
by Kenneth R. Hoover ... [and others]
Cengage Learning, 2004
Buku Teks
Macridis, Roy C., author
Little, Brown, 1983
Buku Teks