Spencer, John H.
IFPA, 1977
Buku Teks
edited by Ernest R. May
George-Braziller, 1963
Buku Teks
Divine, Robert A., author
New Viewpoints, 1974
Buku Teks
Lippmann, Walter, author
Little, Brown, 1943.
Buku Teks
Rosati, Jerel A., 1953-, author
Wadsworth, 2007
Buku Teks