Graber, Mark A., author
Oxford University Press, 2015
Buku Teks
Fisher, Louis, author
McGraw-Hill, 1988
Buku Teks
Tribe, Laurence H., author
Foundation Press, 1988
Buku Teks
Tribe, Laurence H., author
Foundation Press, 1978
Buku Teks
Oceana Publications, 1958
Buku Teks