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