Hutchinson, 1959
Buku Referensi
Ewing, J.H., editor
Dell Publishing, 1964
Buku Teks
editors, Donald D. Carr, Norman Herz
Pergamon Press, 1989
Buku Referensi
Beckett, Kenneth A., author
Grolier International, 1984
Buku Referensi
Raymond J. Corsini, editor
Wiley, 1987
Buku Referensi