Smith, David N.
Ballinger, 1975
Buku Teks
Weiss, John
Prentice-Hall, 1995
Buku Teks
edited by William R. Cline and Sidney Weintraub
Washington, D.C. , Brooklins Institution
Buku Teks
Mason, Edward S.
Fordham University Press, 1958
Buku Teks
Blades, Derek W.
Development Centre of the Organisation for Economic Co-operation and Development, 1974
Buku Teks