Jackson, Grdon E.
Prentice-Hall, 1993
Buku Referensi
Hanslove, Kurt L.
Cornell University , 1967
Buku Teks
Metz, Harold W.
The Brookings Institution, 1945
Buku Teks
Gould, William B., IV
MIT Press, 1982
Buku Teks
Leslie, Douglas L.
West Publishing, 1992
Buku Teks