Francis, Philip H.
AMACOM, 1977
Buku Teks
Howard, Keith
MCB University Press, 1990
Buku Referensi
White, P.A.F.
Macmillan, 1975
Buku Teks
McLeod, T. S.
Gower Press, 1971
Buku Teks
Gerstenfeld, Arthur
California Addison-Wesley Publishing , 1970
Buku Teks