Nathan, James A
Little, Brown, 1983
Buku Teks
Thompson, Kenneth W., author
Princeton University Press, 1960
Buku Teks
Karp, Walter, author
Harper & Row, 1979
Buku Teks
Brown, Seyom, author
Brookings institution Press, 2003
Buku Teks
Easton, David, author
Knopf, 1971
Buku Teks